[cc0 oot] z_vis* (#2782)

* [cc0 oot] z_vis*

* bss

* docs

* fixup

* further vis docs

* add FbFilterType enum

* bss

* gfxP

6 files changed, 204 insertions, 258 deletions

diff --git a/src/code/game.c b/src/code/game.c
index 1636633f9..ae03573ef 100644
--- a/src/code/game.c
+++ b/src/code/game.c
@@ -35,9 +35,9 @@
 #pragma increment_block_number "gc-eu:0 gc-eu-mq:0 gc-jp:0 gc-jp-ce:0 gc-jp-mq:0 gc-us:0 gc-us-mq:0"
 
 SpeedMeter D_801664D0;
-VisCvg sVisCvg;
-VisZBuf sVisZBuf;
-VisMono sVisMono;
+VisCvg sGameStateVisCvg;
+VisZBuffer sGameStateVisZBuffer;
+VisMono sGameStateVisMono;
 ViMode sViMode;
 
 #if DEBUG_FEATURES
@@ -61,38 +61,37 @@ void GameState_FaultPrint(void) {
 void GameState_SetFBFilter(Gfx** gfxP) {
     Gfx* gfx = *gfxP;
 
-    if ((R_FB_FILTER_TYPE >= FB_FILTER_CVG_RGB) && (R_FB_FILTER_TYPE <= FB_FILTER_CVG_RGB_FOG)) {
-        // Visualize coverage
-        sVisCvg.vis.type = FB_FILTER_TO_CVG_TYPE(R_FB_FILTER_TYPE);
-        sVisCvg.vis.primColor.r = R_FB_FILTER_PRIM_COLOR(0);
-        sVisCvg.vis.primColor.g = R_FB_FILTER_PRIM_COLOR(1);
-        sVisCvg.vis.primColor.b = R_FB_FILTER_PRIM_COLOR(2);
-        sVisCvg.vis.primColor.a = R_FB_FILTER_A;
-        VisCvg_Draw(&sVisCvg, &gfx);
-    } else if ((R_FB_FILTER_TYPE == FB_FILTER_ZBUF_IA) || (R_FB_FILTER_TYPE == FB_FILTER_ZBUF_RGBA)) {
-        // Visualize z-buffer
-        sVisZBuf.vis.type = (R_FB_FILTER_TYPE == FB_FILTER_ZBUF_RGBA);
-        sVisZBuf.vis.primColor.r = R_FB_FILTER_PRIM_COLOR(0);
-        sVisZBuf.vis.primColor.g = R_FB_FILTER_PRIM_COLOR(1);
-        sVisZBuf.vis.primColor.b = R_FB_FILTER_PRIM_COLOR(2);
-        sVisZBuf.vis.primColor.a = R_FB_FILTER_A;
-        sVisZBuf.vis.envColor.r = R_FB_FILTER_ENV_COLOR(0);
-        sVisZBuf.vis.envColor.g = R_FB_FILTER_ENV_COLOR(1);
-        sVisZBuf.vis.envColor.b = R_FB_FILTER_ENV_COLOR(2);
-        sVisZBuf.vis.envColor.a = R_FB_FILTER_A;
-        VisZBuf_Draw(&sVisZBuf, &gfx);
-    } else if (R_FB_FILTER_TYPE == FB_FILTER_MONO) {
-        // Monochrome filter
-        sVisMono.vis.type = 0;
-        sVisMono.vis.primColor.r = R_FB_FILTER_PRIM_COLOR(0);
-        sVisMono.vis.primColor.g = R_FB_FILTER_PRIM_COLOR(1);
-        sVisMono.vis.primColor.b = R_FB_FILTER_PRIM_COLOR(2);
-        sVisMono.vis.primColor.a = R_FB_FILTER_A;
-        sVisMono.vis.envColor.r = R_FB_FILTER_ENV_COLOR(0);
-        sVisMono.vis.envColor.g = R_FB_FILTER_ENV_COLOR(1);
-        sVisMono.vis.envColor.b = R_FB_FILTER_ENV_COLOR(2);
-        sVisMono.vis.envColor.a = R_FB_FILTER_A;
-        VisMono_Draw(&sVisMono, &gfx);
+    if ((R_FB_FILTER_TYPE >= FB_FILTER_TYPE_VISCVG_TYPE_MODULATE_FB) &&
+        (R_FB_FILTER_TYPE <= FB_FILTER_TYPE_VISCVG_TYPE_MODULATE_FB_ADDITIVE_COLOR)) {
+        sGameStateVisCvg.params.type = R_FB_FILTER_TYPE;
+        sGameStateVisCvg.params.color1.r = R_FB_FILTER_COLOR1(0);
+        sGameStateVisCvg.params.color1.g = R_FB_FILTER_COLOR1(1);
+        sGameStateVisCvg.params.color1.b = R_FB_FILTER_COLOR1(2);
+        sGameStateVisCvg.params.color1.a = R_FB_FILTER_A;
+        VisCvg_Draw(&sGameStateVisCvg, &gfx);
+    } else if ((R_FB_FILTER_TYPE == FB_FILTER_TYPE_VISZBUFFER_AS_IA16) ||
+               (R_FB_FILTER_TYPE == FB_FILTER_TYPE_VISZBUFFER_AS_RGBA16)) {
+        sGameStateVisZBuffer.params.type = (R_FB_FILTER_TYPE == FB_FILTER_TYPE_VISZBUFFER_AS_RGBA16);
+        sGameStateVisZBuffer.params.color1.r = R_FB_FILTER_COLOR1(0);
+        sGameStateVisZBuffer.params.color1.g = R_FB_FILTER_COLOR1(1);
+        sGameStateVisZBuffer.params.color1.b = R_FB_FILTER_COLOR1(2);
+        sGameStateVisZBuffer.params.color1.a = R_FB_FILTER_A;
+        sGameStateVisZBuffer.params.color2.r = R_FB_FILTER_COLOR2(0);
+        sGameStateVisZBuffer.params.color2.g = R_FB_FILTER_COLOR2(1);
+        sGameStateVisZBuffer.params.color2.b = R_FB_FILTER_COLOR2(2);
+        sGameStateVisZBuffer.params.color2.a = R_FB_FILTER_A;
+        VisZBuffer_Draw(&sGameStateVisZBuffer, &gfx);
+    } else if (R_FB_FILTER_TYPE == FB_FILTER_TYPE_VISMONO) {
+        sGameStateVisMono.params.type = 0;
+        sGameStateVisMono.params.color1.r = R_FB_FILTER_COLOR1(0);
+        sGameStateVisMono.params.color1.g = R_FB_FILTER_COLOR1(1);
+        sGameStateVisMono.params.color1.b = R_FB_FILTER_COLOR1(2);
+        sGameStateVisMono.params.color1.a = R_FB_FILTER_A;
+        sGameStateVisMono.params.color2.r = R_FB_FILTER_COLOR2(0);
+        sGameStateVisMono.params.color2.g = R_FB_FILTER_COLOR2(1);
+        sGameStateVisMono.params.color2.b = R_FB_FILTER_COLOR2(2);
+        sGameStateVisMono.params.color2.a = R_FB_FILTER_A;
+        VisMono_Draw(&sGameStateVisMono, &gfx);
     }
     *gfxP = gfx;
 }
@@ -498,9 +497,9 @@ void GameState_Init(GameState* gameState, GameStateFunc init, GraphicsContext* g
 
     startTime = endTime;
     LOG_UTILS_CHECK_NULL_POINTER("this->cleanup", gameState->destroy, "../game.c", 1088);
-    VisCvg_Init(&sVisCvg);
-    VisZBuf_Init(&sVisZBuf);
-    VisMono_Init(&sVisMono);
+    VisCvg_Init(&sGameStateVisCvg);
+    VisZBuffer_Init(&sGameStateVisZBuffer);
+    VisMono_Init(&sGameStateVisMono);
     if ((R_VI_MODE_EDIT_STATE == VI_MODE_EDIT_STATE_INACTIVE) || !DEBUG_FEATURES) {
         ViMode_Init(&sViMode);
     }
@@ -529,9 +528,9 @@ void GameState_Destroy(GameState* gameState) {
     }
     Rumble_Destroy();
     SpeedMeter_Destroy(&D_801664D0);
-    VisCvg_Destroy(&sVisCvg);
-    VisZBuf_Destroy(&sVisZBuf);
-    VisMono_Destroy(&sVisMono);
+    VisCvg_Destroy(&sGameStateVisCvg);
+    VisZBuffer_Destroy(&sGameStateVisZBuffer);
+    VisMono_Destroy(&sGameStateVisMono);
     if ((R_VI_MODE_EDIT_STATE == VI_MODE_EDIT_STATE_INACTIVE) || !DEBUG_FEATURES) {
         ViMode_Destroy(&sViMode);
     }
diff --git a/src/code/z_play.c b/src/code/z_play.c
index 8d73e9e56..ad0023e2d 100644
--- a/src/code/z_play.c
+++ b/src/code/z_play.c
@@ -47,12 +47,12 @@
 #include "save.h"
 #include "vis.h"
 
-#pragma increment_block_number "gc-eu:224 gc-eu-mq:224 gc-jp:224 gc-jp-ce:224 gc-jp-mq:224 gc-us:224 gc-us-mq:224" \
-                               "ique-cn:224 ntsc-1.0:240 ntsc-1.1:240 ntsc-1.2:240 pal-1.0:240 pal-1.1:240"
+#pragma increment_block_number "gc-eu:218 gc-eu-mq:218 gc-jp:218 gc-jp-ce:218 gc-jp-mq:218 gc-us:218 gc-us-mq:218" \
+                               "ique-cn:218 ntsc-1.0:218 ntsc-1.1:218 ntsc-1.2:218 pal-1.0:218 pal-1.1:218"
 
 TransitionTile gTransitionTile;
 s32 gTransitionTileState;
-VisMono gPlayVisMono;
+VisMono sPlayVisMono;
 Color_RGBA8_u32 gVisMonoColor;
 
 #if DEBUG_FEATURES
@@ -261,7 +261,7 @@ void Play_Destroy(GameState* thisx) {
 
     Letterbox_Destroy();
     TransitionFade_Destroy(&this->transitionFadeFlash);
-    VisMono_Destroy(&gPlayVisMono);
+    VisMono_Destroy(&sPlayVisMono);
 
     if (gSaveContext.save.linkAge != this->linkAgeOnLoad) {
         Inventory_SwapAgeEquipment();
@@ -482,7 +482,7 @@ void Play_Init(GameState* thisx) {
     TransitionFade_SetType(&this->transitionFadeFlash, TRANS_INSTANCE_TYPE_FADE_FLASH);
     TransitionFade_SetColor(&this->transitionFadeFlash, RGBA8(160, 160, 160, 255));
     TransitionFade_Start(&this->transitionFadeFlash);
-    VisMono_Init(&gPlayVisMono);
+    VisMono_Init(&sPlayVisMono);
     gVisMonoColor.a = 0;
     CutsceneFlags_UnsetAll(this);
 
@@ -1217,8 +1217,8 @@ void Play_Draw(PlayState* this) {
             if (gVisMonoColor.a > 0)
 #endif
             {
-                gPlayVisMono.vis.primColor.rgba = gVisMonoColor.rgba;
-                VisMono_Draw(&gPlayVisMono, &gfxP);
+                sPlayVisMono.params.color1.rgba = gVisMonoColor.rgba;
+                VisMono_Draw(&sPlayVisMono, &gfxP);
             }
 
             gSPEndDisplayList(gfxP++);
diff --git a/src/code/z_viscvg.c b/src/code/z_viscvg.c
index 1616b661c..236c0c052 100644
--- a/src/code/z_viscvg.c
+++ b/src/code/z_viscvg.c
@@ -1,104 +1,71 @@
 /**
- * @file z_viscvg.c
- *
- * This file implements full-screen frame buffer effects involving the visualization of Coverage in various ways.
- *
- * Coverage is roughly how much of a pixel is covered by a primitive; the final coverage for a frame is stored in the
- * color image alpha component where it is used for antialiasing, see PreRender.c and §15 of the programming manual for
- * details.
- *
- * To understand this file, it is helpful to remember that A_MEM is essentially synonymous with coverage, and that
- * `GBL_c1/2(p, a, m, b)` usually represents the RDP blender calculation `(p * a + m * b)`.
- * Note the division step that is often included in the blender calculation is omitted; the division is skipped if
- * force blending (FORCE_BL) is set, which is the case for all render modes used in this file.
- *
- * Coverage is full when not on an edge, while on an edge it is usually lower. Since coverage is treated as an alpha
- * value, edges of primitives where coverage is lower will show up darker than primitive interiors in all of the
- * available modes.
- *
- * Coverage is abbreviated to "cvg"; "FB RGB" ("framebuffer red/green/blue") is the color the pixel originally had
- * before the filter is applied.
+ * This file implements framebuffer effects relying on coverage.
+ * Coverage's primary use is performing antialiasing: it basically tracks how much of a pixel is covered by its current
+ * color. Coverage is stored in a rgba16 framebuffer as a 3 bits value.
+ * Coverage is typically partial on geometry outer edges and full elsewhere: this makes the framebuffer effects here
+ * usually highlight silhouettes.
  */
 
+#include "ultra64.h"
 #include "gfx.h"
 #include "vis.h"
 
-/**
- * Draws only coverage: does not retain any of the original pixel RGB, primColor is used as background color.
- */
-Gfx sCoverageOnlyDL[] = {
+Gfx sVisCvgModulateBlendColorDL[] = {
     gsDPSetOtherMode(G_AD_PATTERN | G_CD_MAGICSQ | G_CK_NONE | G_TC_CONV | G_TF_POINT | G_TT_NONE | G_TL_TILE |
                          G_TD_CLAMP | G_TP_NONE | G_CYC_1CYCLE | G_PM_NPRIMITIVE,
                      G_AC_NONE | G_ZS_PRIM | G_RM_VISCVG | G_RM_VISCVG2),
-    // (blendColor RGB) * (cvg)
     gsDPFillRectangle(0, 0, SCREEN_WIDTH - 1, SCREEN_HEIGHT - 1),
     gsDPPipeSync(),
     gsDPSetBlendColor(0, 0, 0, 8),
     gsSPEndDisplayList(),
 };
 
-/**
- * Draws fog + coverage * RGB of pixels
- *
- * @bug This easily overflows the blender because the fog value is added to the coverage value.
- */
-Gfx sCoverageRGBFogDL[] = {
+Gfx sVisCvgModulateFramebufferAdditiveFogDL[] = {
     gsDPSetOtherMode(G_AD_PATTERN | G_CD_MAGICSQ | G_CK_NONE | G_TC_CONV | G_TF_POINT | G_TT_NONE | G_TL_TILE |
                          G_TD_CLAMP | G_TP_NONE | G_CYC_1CYCLE | G_PM_NPRIMITIVE,
                      G_AC_NONE | G_ZS_PRIM | IM_RD | CVG_DST_CLAMP | ZMODE_OPA | FORCE_BL |
+                         // Note: additive blending often overflows the blender, causing visual bugs
                          GBL_c1(G_BL_CLR_FOG, G_BL_A_FOG, G_BL_CLR_MEM, G_BL_A_MEM) |
                          GBL_c2(G_BL_CLR_FOG, G_BL_A_FOG, G_BL_CLR_MEM, G_BL_A_MEM)),
-    // (fog RGB) * (fog alpha) + (FB RGB) * (cvg)
     gsDPFillRectangle(0, 0, SCREEN_WIDTH - 1, SCREEN_HEIGHT - 1),
     gsSPEndDisplayList(),
 };
 
-/**
- * Draws coverage and RGB of pixels
- */
-Gfx sCoverageRGBDL[] = {
+Gfx sVisCvgModulateFramebufferDL[] = {
     gsDPSetOtherMode(G_AD_PATTERN | G_CD_MAGICSQ | G_CK_NONE | G_TC_CONV | G_TF_POINT | G_TT_NONE | G_TL_TILE |
                          G_TD_CLAMP | G_TP_NONE | G_CYC_1CYCLE | G_PM_NPRIMITIVE,
                      G_AC_NONE | G_ZS_PRIM | IM_RD | CVG_DST_CLAMP | ZMODE_OPA | FORCE_BL |
                          GBL_c1(G_BL_CLR_IN, G_BL_0, G_BL_CLR_MEM, G_BL_A_MEM) |
                          GBL_c2(G_BL_CLR_IN, G_BL_0, G_BL_CLR_MEM, G_BL_A_MEM)),
-    // (FB RGB) * (cvg)
     gsDPFillRectangle(0, 0, SCREEN_WIDTH - 1, SCREEN_HEIGHT - 1),
     gsSPEndDisplayList(),
 };
 
-/**
- * Two stage filtering:
- *
- * 1. Apply a uniform color filter by transparently blending primColor with original frame. The "cloud surface"
- * RenderMode is used to preserve the coverage for the second stage.
- * 2. Second half is the same as `sCoverageRGBDL`'s, i.e. (RGB from stage 1) * cvg
- */
-Gfx sCoverageRGBUniformDL[] = {
+Gfx sVisCvgFadeToPrimAndModulateFramebuffer[] = {
+    // Fade the framebuffer towards prim color
     gsDPSetCombineMode(G_CC_PRIMITIVE, G_CC_PRIMITIVE),
     gsDPSetOtherMode(G_AD_NOTPATTERN | G_CD_DISABLE | G_CK_NONE | G_TC_CONV | G_TF_POINT | G_TT_NONE | G_TL_TILE |
                          G_TD_CLAMP | G_TP_NONE | G_CYC_1CYCLE | G_PM_NPRIMITIVE,
+                     // Note: G_RM_CLD_SURF sets CVG_DST_SAVE which preserves coverage
                      G_AC_NONE | G_ZS_PRIM | G_RM_CLD_SURF | G_RM_CLD_SURF2),
-    // stage 1 color = (primColor RGB) * (primColor Alpha) + (FB RGB) * (1 - primColor Alpha)
     gsDPFillRectangle(0, 0, SCREEN_WIDTH - 1, SCREEN_HEIGHT - 1),
-
+    // Like sVisCvgModulateFramebufferDL
     gsDPSetOtherMode(G_AD_PATTERN | G_CD_MAGICSQ | G_CK_NONE | G_TC_CONV | G_TF_POINT | G_TT_NONE | G_TL_TILE |
                          G_TD_CLAMP | G_TP_NONE | G_CYC_1CYCLE | G_PM_NPRIMITIVE,
                      G_AC_NONE | G_ZS_PRIM | IM_RD | CVG_DST_CLAMP | ZMODE_OPA | FORCE_BL |
                          GBL_c1(G_BL_CLR_IN, G_BL_0, G_BL_CLR_MEM, G_BL_A_MEM) |
                          GBL_c2(G_BL_CLR_IN, G_BL_0, G_BL_CLR_MEM, G_BL_A_MEM)),
-    // final color = (stage 1 RGB) * (cvg)
     gsDPFillRectangle(0, 0, SCREEN_WIDTH - 1, SCREEN_HEIGHT - 1),
     gsSPEndDisplayList(),
 };
 
 void VisCvg_Init(VisCvg* this) {
-    this->vis.type = FB_FILTER_NONE;
-    this->vis.scissorType = VIS_NO_SETSCISSOR;
-    this->vis.primColor.r = 255;
-    this->vis.primColor.g = 255;
-    this->vis.primColor.b = 255;
-    this->vis.primColor.a = 255;
+    this->params.type = VISCVG_TYPE_NOP;
+    this->params.setScissor = false;
+    this->params.color1.r = 255;
+    this->params.color1.g = 255;
+    this->params.color1.b = 255;
+    this->params.color1.a = 255;
 }
 
 void VisCvg_Destroy(VisCvg* this) {
@@ -108,36 +75,31 @@ void VisCvg_Draw(VisCvg* this, Gfx** gfxP) {
     Gfx* gfx = *gfxP;
 
     gDPPipeSync(gfx++);
+    // Set full dz, see comment in PreRender_FetchFbufCoverage for details.
     gDPSetPrimDepth(gfx++, 0xFFFF, 0xFFFF);
 
-    if (this->vis.scissorType == VIS_SETSCISSOR) {
+    if (this->params.setScissor == true) {
         gDPSetScissor(gfx++, G_SC_NON_INTERLACE, 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT);
     }
 
-    switch (this->vis.type) {
-        case FB_FILTER_CVG_RGB:
-            gSPDisplayList(gfx++, sCoverageRGBDL);
-            break;
-
-        case FB_FILTER_CVG_RGB_UNIFORM:
-            // Set primitive color for uniform color filter in custom RenderMode
-            gDPSetColor(gfx++, G_SETPRIMCOLOR, this->vis.primColor.rgba);
-            gSPDisplayList(gfx++, sCoverageRGBUniformDL);
+    switch (this->params.type) {
+        case VISCVG_TYPE_MODULATE_FB:
+            gSPDisplayList(gfx++, sVisCvgModulateFramebufferDL);
             break;
 
-        case FB_FILTER_CVG_ONLY:
-            // Set background color for G_RM_VISCVG
-            gDPSetColor(gfx++, G_SETBLENDCOLOR, this->vis.primColor.rgba);
-            gSPDisplayList(gfx++, sCoverageOnlyDL);
+        case VISCVG_TYPE_FADE_AND_MODULATE_FB:
+            gDPSetColor(gfx++, G_SETPRIMCOLOR, this->params.color1.rgba);
+            gSPDisplayList(gfx++, sVisCvgFadeToPrimAndModulateFramebuffer);
             break;
 
-        case FB_FILTER_CVG_RGB_FOG:
-            // Set fog color for custom RenderMode, needs to be close to 0 to not overflow
-            gDPSetColor(gfx++, G_SETFOGCOLOR, this->vis.primColor.rgba);
-            gSPDisplayList(gfx++, sCoverageRGBFogDL);
+        case VISCVG_TYPE_MODULATE_COLOR:
+            gDPSetColor(gfx++, G_SETBLENDCOLOR, this->params.color1.rgba);
+            gSPDisplayList(gfx++, sVisCvgModulateBlendColorDL);
             break;
 
-        default:
+        case VISCVG_TYPE_MODULATE_FB_ADDITIVE_COLOR:
+            gDPSetColor(gfx++, G_SETFOGCOLOR, this->params.color1.rgba);
+            gSPDisplayList(gfx++, sVisCvgModulateFramebufferAdditiveFogDL);
             break;
     }
 
diff --git a/src/code/z_vismono.c b/src/code/z_vismono.c
index 632d00a6e..bd7950781 100644
--- a/src/code/z_vismono.c
+++ b/src/code/z_vismono.c
@@ -1,11 +1,14 @@
 /**
- * @file z_vismono.c
+ * Color frame buffer effect to desaturate the colors.
  *
- * This file implements a full-screen framebuffer effect for desaturating the contents of the framebuffer image.
+ * The result of the desaturation is used to LERP from color2 (0) to color1 (1).
+ * In the simplest case, to get a grayscale result, set color1 to white and color2 to black.
  *
- * Broadly, this effect is achieved by reinterpreting the contents of the RGBA16 color image as indices into an IA16
- * color palette that converts each color into the desaturated equivalent. More precise details can be found in inline
- * comments.
+ * This effect is achieved by making the RDP read the rgba16 framebuffer as a ci8 texture using a specific ia16 palette.
+ * For every two-bytes pixel in the rgba16 framebuffer, the palette maps in particular an intensity to the high byte and
+ * an alpha value to the low byte. The sum of those intensity and alpha value corresponds to the gray level of the
+ * desaturated color. This sum is done by the RDP with a clever setup of texture tiles and an adequate combiner.
+ * See the rest of the file for specifics.
  */
 
 #include "libc64/malloc.h"
@@ -17,7 +20,7 @@
 
 // Height of the fragments the color frame buffer (CFB) is split into.
 // It is the maximum amount of lines such that all rgba16 SCREEN_WIDTH-long lines fit into
-// the half of TMEM dedicated to color-indexed data.
+// the half of tmem dedicated to color-indexed data.
 #define VISMONO_CFBFRAG_HEIGHT ((TMEM_SIZE / 2) / (SCREEN_WIDTH * G_IM_SIZ_16b_BYTES))
 
 // Maximum size of the dlist written by `VisMono_DesaturateDList`.
@@ -37,16 +40,16 @@ extern u16 D_0F000000[];
 
 void VisMono_Init(VisMono* this) {
     bzero(this, sizeof(VisMono));
-    this->vis.type = 0;
-    this->vis.scissorType = VIS_NO_SETSCISSOR;
-    this->vis.primColor.r = 255;
-    this->vis.primColor.g = 255;
-    this->vis.primColor.b = 255;
-    this->vis.primColor.a = 255;
-    this->vis.envColor.r = 0;
-    this->vis.envColor.g = 0;
-    this->vis.envColor.b = 0;
-    this->vis.envColor.a = 0;
+    this->params.type = 0;
+    this->params.setScissor = false;
+    this->params.color1.r = 255;
+    this->params.color1.g = 255;
+    this->params.color1.b = 255;
+    this->params.color1.a = 255;
+    this->params.color2.r = 0;
+    this->params.color2.g = 0;
+    this->params.color2.b = 0;
+    this->params.color2.a = 0;
 }
 
 void VisMono_Destroy(VisMono* this) {
@@ -105,8 +108,7 @@ Gfx* VisMono_DesaturateDList(VisMono* this, Gfx* gfx) {
 
         // Set texel 1 to be a CI8 image with width `SCREEN_WIDTH * 2` and height `VISMONO_CFBFRAG_HEIGHT`
         // Its position in texture image space is shifted along +S by 1
-        // Note the palette index for this tile has also been incremented from 0 to 1, however the palette index is
-        // ignored for CI8 texture sampling.
+        // (palette is set to 1 here but that's ignored in the case of CI8 where there is only one palette)
         gDPSetTile(gfx++, G_IM_FMT_CI, G_IM_SIZ_8b, SCREEN_WIDTH * 2 * G_IM_SIZ_8b_LINE_BYTES / 8, 0x0, 1, 1,
                    G_TX_NOMIRROR | G_TX_CLAMP, 0, 0, G_TX_NOMIRROR | G_TX_CLAMP, 0, 0);
         gDPSetTileSize(gfx++, 1, 1 << 2, 0, (SCREEN_WIDTH * 2) << 2, (height - 1) << 2);
@@ -171,12 +173,12 @@ void VisMono_Draw(VisMono* this, Gfx** gfxP) {
 
     gDPPipeSync(gfx++);
 
-    if (this->vis.scissorType == VIS_SETSCISSOR) {
+    if (this->params.setScissor == true) {
         gDPSetScissor(gfx++, G_SC_NON_INTERLACE, 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT);
     }
 
-    gDPSetColor(gfx++, G_SETPRIMCOLOR, this->vis.primColor.rgba);
-    gDPSetColor(gfx++, G_SETENVCOLOR, this->vis.envColor.rgba);
+    gDPSetColor(gfx++, G_SETPRIMCOLOR, this->params.color1.rgba);
+    gDPSetColor(gfx++, G_SETENVCOLOR, this->params.color2.rgba);
 
     gDPLoadTLUT_pal256(gfx++, tlut);
 
diff --git a/src/code/z_viszbuf.c b/src/code/z_viszbuf.c
deleted file mode 100644
index aa7228974..000000000
--- a/src/code/z_viszbuf.c
+++ /dev/null
@@ -1,117 +0,0 @@
-/**
- * @file z_viszbuf.c
- *
- * This file implements a full-screen framebuffer effect for visualizing the z-buffer (AKA depth buffer), using either
- * cycling RGBA or a single fading color.
- *
- * This is done by reading the z-buffer as if it were a color image, the format of which is specified by the selected
- * vis type:
- *  - VIS_ZBUF_TYPE_IA   : Produces a monotonic fade from primColor to envColor as depth increases.
- *  - VIS_ZBUF_TYPE_RGBA : Produces vibrant almost-periodic-looking bands.
- *
- * In both cases this occurs because of the format the depth information takes: it is 18-bit, and is a nonnegative
- * floating-point number with
- *     bbb      mmmmmmmmmmm dd|dd
- *     exponent mantissa    dz value (only first 16 bits visible to CPU, the least significant 2 bits of dz are ignored)
- *
- * Reading z-buffer as IA16:
- *     bbbmmmmm mmmmmmdd
- *     iiiiiiii aaaaaaaa
- *
- * Since floating-point numbers of this format have the same ordering as their binary/hex representation, increasing
- * the depth also increases the intensity in the IA16 representation and hence the interpolation parameter used to
- * combine primColor and envColor. The alpha is ignored by the RenderMode.
- *
- * Reading z-buffer as RGBA16:
- *     bbbmm mmmmm mmmmd d
- *     rrrrr ggggg bbbbb a
- *
- * The red increases monotonically with the depth. The significant visible oscillation is the green component, because
- * it rolls over every time the second-most-significant bit of the mantissa increments. The blue component oscillates
- * too rapidly to be particularly visible (it rolls over when the 7th-most-significant bit increments). The alpha is
- * again ignored by the RenderMode.
- */
-
-#include "gfx.h"
-#include "vis.h"
-
-// Height of the fragments the z-buffer is split into.
-// It is the maximum amount of lines such that all rgba16 SCREEN_WIDTH-long lines fit into TMEM.
-#define VISZBUF_ZBUFFRAG_HEIGHT (TMEM_SIZE / (SCREEN_WIDTH * G_IM_SIZ_16b_BYTES))
-
-// z-buffer
-extern u16 D_0E000000[];
-
-/**
- * Initialise to IA type with white and black as default colors.
- */
-void VisZBuf_Init(VisZBuf* this) {
-    this->vis.type = VIS_ZBUF_TYPE_IA;
-    this->vis.scissorType = VIS_NO_SETSCISSOR;
-
-    this->vis.primColor.r = 255;
-    this->vis.primColor.g = 255;
-    this->vis.primColor.b = 255;
-    this->vis.primColor.a = 255;
-
-    // clang-format off
-    this->vis.envColor.r = 0; \
-    this->vis.envColor.g = 0; \
-    this->vis.envColor.b = 0; \
-    this->vis.envColor.a = 255;
-    // clang-format on
-}
-
-void VisZBuf_Destroy(VisZBuf* this) {
-}
-
-void VisZBuf_Draw(VisZBuf* this, Gfx** gfxP) {
-    Gfx* gfx = *gfxP;
-    s32 pad;
-    u16* zbufFrag = D_0E000000;
-    s32 fmt;
-    s32 y;
-    s32 height;
-
-    if (this->vis.type == VIS_ZBUF_TYPE_IA) {
-        fmt = G_IM_FMT_IA;
-    } else { // VIS_ZBUF_TYPE_RGBA
-        fmt = G_IM_FMT_RGBA;
-    }
-
-    height = VISZBUF_ZBUFFRAG_HEIGHT;
-
-    gDPPipeSync(gfx++);
-    // Scissoring is only required if the scissor has not been set prior.
-    if (this->vis.scissorType == VIS_SETSCISSOR) {
-        gDPSetScissor(gfx++, G_SC_NON_INTERLACE, 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT);
-    }
-
-    // No palette so can use all of TMEM.
-    // G_RM_OPA_SURF discards all information previously in the pixel, and the current alpha, leaving only the color
-    // from this filter.
-    gDPSetOtherMode(gfx++,
-                    G_AD_DISABLE | G_CD_MAGICSQ | G_CK_NONE | G_TC_FILT | G_TF_POINT | G_TT_NONE | G_TL_TILE |
-                        G_TD_CLAMP | G_TP_NONE | G_CYC_1CYCLE | G_PM_NPRIMITIVE,
-                    G_AC_NONE | G_ZS_PRIM | G_RM_OPA_SURF | G_RM_OPA_SURF2);
-
-    // LERP between primColor and envColor in 1-cycle mode using the z-buffer value.
-    gDPSetCombineLERP(gfx++, PRIMITIVE, ENVIRONMENT, TEXEL0, ENVIRONMENT, PRIMITIVE, ENVIRONMENT, TEXEL0, ENVIRONMENT,
-                      PRIMITIVE, ENVIRONMENT, TEXEL0, ENVIRONMENT, PRIMITIVE, ENVIRONMENT, TEXEL0, ENVIRONMENT);
-    gDPSetColor(gfx++, G_SETPRIMCOLOR, this->vis.primColor.rgba);
-    gDPSetColor(gfx++, G_SETENVCOLOR, this->vis.envColor.rgba);
-
-    for (y = 0; y <= SCREEN_HEIGHT - height; y += height) {
-        // Load a few lines of the z-buffer, as many as can fit in TMEM at once.
-        gDPLoadTextureBlock(gfx++, zbufFrag, fmt, G_IM_SIZ_16b, SCREEN_WIDTH, height, 0, G_TX_NOMIRROR | G_TX_CLAMP,
-                            G_TX_NOMIRROR | G_TX_CLAMP, G_TX_NOMASK, G_TX_NOMASK, G_TX_NOLOD, G_TX_NOLOD);
-
-        // Overwrite them with the calculated colors.
-        gSPTextureRectangle(gfx++, 0, y << 2, SCREEN_WIDTH << 2, (y + height) << 2, G_TX_RENDERTILE, 0, 0, 1 << 10,
-                            1 << 10);
-        zbufFrag += SCREEN_WIDTH * height;
-    }
-
-    gDPPipeSync(gfx++);
-    *gfxP = gfx;
-}
diff --git a/src/code/z_viszbuffer.c b/src/code/z_viszbuffer.c
new file mode 100644
index 000000000..fa37f1440
--- /dev/null
+++ b/src/code/z_viszbuffer.c
@@ -0,0 +1,100 @@
+/**
+ * This file implements a framebuffer effect relying on the depth buffer (Z buffer).
+ * It merely allows LERPing between two colors (from color2 to color1), using the Z buffer bytes (interpreted as either
+ * ia16 or rgba16 depending on the type being 0 or not) as the factor.
+ *
+ * Z buffer values are two bytes each. They are floating point, which makes the effect not that interesting for an
+ * actual application as that doesn't map well to be interpreted as ia16 or rgba16, though some discontinuous gradients
+ * can be seen.
+ *
+ * The bit layout of Z buffer values is:
+ * 0bEEEM_MMMM_MMMM_MMDD
+ * Where E is the 3 exponent bits, M is the 11 mantissa bits,
+ * and D is 2 of the 4 dz value bits (the remaining two are stored in the "hidden" 9th bit of each byte).
+ * In 3D space, Z values increase from front (near plane) to back (far plane).
+ *
+ * Interpreted as ia16:
+ * 0bIIII_IIII_AAAA_AAAA
+ * The intensity channel takes its value from the exponent bits and the high mantissa bits, so it continuously increases
+ * from front to back.
+ * The alpha channel mostly takes its value from the lowest mantissa bits, so it increases from front to back but also
+ * rolls over frequently.
+ * This can be observed in-game by setting color1 to white and color2 to black.
+ * From front to back, the intensity gradient is a continuous increase.
+ * The alpha is ignored due to the render mode VisZBuffer uses.
+ *
+ * Interpreted as rgba16:
+ * 0bRRRR_RGGG_GGBB_BBBA
+ * The red channel mostly takes its value from the exponent bits, so it continuously increases from front to back.
+ * The green channel takes its value from the middle mantissa bits, so it increases from front to back but also rolls
+ * over frequently.
+ * The blue channel mostly takes its value from the lowest mantissa bits, so it increases from front to back and also
+ * rolls over even more frequently.
+ * This can be observed in-game by setting color1 to white and color2 to black.
+ * From front to back, the gradients for each color channel are then:
+ * - red: continuous increase
+ * - green: discontinuous succession of continuous increases
+ * - blue: like green but even higher frequency
+ */
+
+#include "ultra64.h"
+#include "gfx.h"
+#include "vis.h"
+
+// z-buffer
+extern u16 D_0E000000[];
+
+void VisZBuffer_Init(VisZBuffer* this) {
+    this->params.type = 0;
+    this->params.setScissor = false;
+    this->params.color1.r = 255;
+    this->params.color1.g = 255;
+    this->params.color1.b = 255;
+    this->params.color1.a = 255;
+
+    // clang-format off
+    this->params.color2.r = 0; \
+    this->params.color2.g = 0; \
+    this->params.color2.b = 0; \
+    this->params.color2.a = 255;
+    // clang-format on
+}
+
+void VisZBuffer_Destroy(VisZBuffer* this) {
+}
+
+void VisZBuffer_Draw(VisZBuffer* this, Gfx** gfxP) {
+    Gfx* gfx = *gfxP;
+    s32 pad;
+    u16* tex = D_0E000000;
+    s32 fmt = this->params.type == 0 ? G_IM_FMT_IA : G_IM_FMT_RGBA;
+    s32 y;
+    s32 height = TMEM_SIZE / (SCREEN_WIDTH * G_IM_SIZ_16b_BYTES);
+
+    gDPPipeSync(gfx++);
+    if (this->params.setScissor == true) {
+        gDPSetScissor(gfx++, G_SC_NON_INTERLACE, 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT);
+    }
+
+    gDPSetOtherMode(gfx++,
+                    G_AD_DISABLE | G_CD_MAGICSQ | G_CK_NONE | G_TC_FILT | G_TF_POINT | G_TT_NONE | G_TL_TILE |
+                        G_TD_CLAMP | G_TP_NONE | G_CYC_1CYCLE | G_PM_NPRIMITIVE,
+                    G_AC_NONE | G_ZS_PRIM | G_RM_OPA_SURF | G_RM_OPA_SURF2);
+    gDPSetCombineLERP(gfx++, PRIMITIVE, ENVIRONMENT, TEXEL0, ENVIRONMENT, PRIMITIVE, ENVIRONMENT, TEXEL0, ENVIRONMENT,
+                      PRIMITIVE, ENVIRONMENT, TEXEL0, ENVIRONMENT, PRIMITIVE, ENVIRONMENT, TEXEL0, ENVIRONMENT);
+
+    gDPSetColor(gfx++, G_SETPRIMCOLOR, this->params.color1.rgba);
+    gDPSetColor(gfx++, G_SETENVCOLOR, this->params.color2.rgba);
+
+    for (y = 0; y <= SCREEN_HEIGHT - height; y += height) {
+        gDPLoadTextureBlock(gfx++, tex, fmt, G_IM_SIZ_16b, SCREEN_WIDTH, height, 0, G_TX_NOMIRROR | G_TX_CLAMP,
+                            G_TX_NOMIRROR | G_TX_CLAMP, G_TX_NOMASK, G_TX_NOMASK, G_TX_NOLOD, G_TX_NOLOD);
+
+        gSPTextureRectangle(gfx++, 0, y << 2, SCREEN_WIDTH << 2, (y + height) << 2, G_TX_RENDERTILE, 0, 0, 1 << 10,
+                            1 << 10);
+        tex += SCREEN_WIDTH * height;
+    }
+
+    gDPPipeSync(gfx++);
+    *gfxP = gfx;
+}