From a2aa8af97395eb2043822db19730a3676127b5b1 Mon Sep 17 00:00:00 2001
From: rdb <git@rdb.name>
Date: Mon, 2 Jan 2023 10:46:48 +0100
Subject: [PATCH] Correctly support 4-component UV coordinates in generated
 shaders

Supports projective UVs, matching fixed-function pipeline behavior
---
 .../glstuff/glGraphicsStateGuardian_src.cxx   | 30 +++++++++----------
 panda/src/pgraphnodes/shaderGenerator.cxx     |  5 +++-
 2 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/panda/src/glstuff/glGraphicsStateGuardian_src.cxx b/panda/src/glstuff/glGraphicsStateGuardian_src.cxx
index 702da1ce2c..687a8bbafb 100644
--- a/panda/src/glstuff/glGraphicsStateGuardian_src.cxx
+++ b/panda/src/glstuff/glGraphicsStateGuardian_src.cxx
@@ -185,16 +185,16 @@ static const string default_vshader =
 #endif
   "in vec4 p3d_Vertex;\n"
   "in vec4 p3d_Color;\n"
-  "in vec2 p3d_MultiTexCoord0;\n"
-  "out vec2 texcoord;\n"
+  "in vec4 p3d_MultiTexCoord0;\n"
+  "out vec3 texcoord;\n"
   "out vec4 color;\n"
 #else
   "#version 100\n"
   "precision mediump float;\n"
   "attribute vec4 p3d_Vertex;\n"
   "attribute vec4 p3d_Color;\n"
-  "attribute vec2 p3d_MultiTexCoord0;\n"
-  "varying vec2 texcoord;\n"
+  "attribute vec4 p3d_MultiTexCoord0;\n"
+  "varying vec3 texcoord;\n"
   "varying lowp vec4 color;\n"
 #endif
   "uniform mat4 p3d_ModelViewProjectionMatrix;\n"
@@ -202,7 +202,7 @@ static const string default_vshader =
   "uniform vec4 p3d_ColorScale;\n"
   "void main(void) {\n"
   "  gl_Position = p3d_ModelViewProjectionMatrix * p3d_Vertex;\n"
-  "  texcoord = (p3d_TextureMatrix * vec4(p3d_MultiTexCoord0.x, p3d_MultiTexCoord0.y, 0, 1)).xy;\n"
+  "  texcoord = (p3d_TextureMatrix * p3d_MultiTexCoord0).xyw;\n"
   "  color = p3d_Color * p3d_ColorScale;\n"
   "}\n";
 
@@ -218,8 +218,8 @@ static const string default_vshader_fp64 =
   "#extension GL_ARB_gpu_shader_fp64 : require\n"
   "in dvec3 p3d_Vertex;\n"
   "in vec4 p3d_Color;\n"
-  "in dvec2 p3d_MultiTexCoord0;\n"
-  "out vec2 texcoord;\n"
+  "in dvec4 p3d_MultiTexCoord0;\n"
+  "out vec3 texcoord;\n"
   "out vec4 color;\n"
   "uniform mat4 p3d_ModelViewMatrix;\n"
   "uniform mat4 p3d_ProjectionMatrix;\n"
@@ -227,7 +227,7 @@ static const string default_vshader_fp64 =
   "uniform vec4 p3d_ColorScale;\n"
   "void main(void) {\n" // Apply proj & modelview in two steps, more precise
   "  gl_Position = vec4(dmat4(p3d_ProjectionMatrix) * (dmat4(p3d_ModelViewMatrix) * dvec4(p3d_Vertex, 1)));\n"
-  "  texcoord = (p3d_TextureMatrix * vec4(p3d_MultiTexCoord0.x, p3d_MultiTexCoord0.y, 0, 1)).xy;\n"
+  "  texcoord = (p3d_TextureMatrix * vec4(p3d_MultiTexCoord0)).xyw;\n"
   "  color = p3d_Color * p3d_ColorScale;\n"
   "}\n";
 
@@ -236,8 +236,8 @@ static const string default_vshader_fp64_gl41 =
   "#version 410\n"
   "in dvec3 p3d_Vertex;\n"
   "in vec4 p3d_Color;\n"
-  "in dvec2 p3d_MultiTexCoord0;\n"
-  "out vec2 texcoord;\n"
+  "in dvec4 p3d_MultiTexCoord0;\n"
+  "out vec3 texcoord;\n"
   "out vec4 color;\n"
   "uniform mat4 p3d_ModelViewMatrix;\n"
   "uniform mat4 p3d_ProjectionMatrix;\n"
@@ -245,7 +245,7 @@ static const string default_vshader_fp64_gl41 =
   "uniform vec4 p3d_ColorScale;\n"
   "void main(void) {\n" // Apply proj & modelview in two steps, more precise
   "  gl_Position = vec4(dmat4(p3d_ProjectionMatrix) * (dmat4(p3d_ModelViewMatrix) * dvec4(p3d_Vertex, 1)));\n"
-  "  texcoord = (p3d_TextureMatrix * vec4(p3d_MultiTexCoord0.x, p3d_MultiTexCoord0.y, 0, 1)).xy;\n"
+  "  texcoord = (p3d_TextureMatrix * vec4(p3d_MultiTexCoord0)).xyw;\n"
   "  color = p3d_Color * p3d_ColorScale;\n"
   "}\n";
 #endif
@@ -257,7 +257,7 @@ static const string default_fshader =
 #else
   "#version 130\n"
 #endif
-  "in vec2 texcoord;\n"
+  "in vec3 texcoord;\n"
   "in vec4 color;\n"
   "out vec4 p3d_FragColor;\n"
   "uniform sampler2D p3d_Texture0;\n"
@@ -265,18 +265,18 @@ static const string default_fshader =
 #else
   "#version 100\n"
   "precision mediump float;\n"
-  "varying vec2 texcoord;\n"
+  "varying vec3 texcoord;\n"
   "varying lowp vec4 color;\n"
   "uniform lowp sampler2D p3d_Texture0;\n"
   "uniform lowp vec4 p3d_TexAlphaOnly;\n"
 #endif
   "void main(void) {\n"
 #ifndef OPENGLES
-  "  p3d_FragColor = texture(p3d_Texture0, texcoord);\n"
+  "  p3d_FragColor = textureProj(p3d_Texture0, texcoord);\n"
   "  p3d_FragColor += p3d_TexAlphaOnly;\n" // Hack for text rendering
   "  p3d_FragColor *= color;\n"
 #else
-  "  gl_FragColor = texture2D(p3d_Texture0, texcoord);\n"
+  "  gl_FragColor = texture2DProj(p3d_Texture0, texcoord);\n"
   "  gl_FragColor += p3d_TexAlphaOnly;\n" // Hack for text rendering
   "  gl_FragColor *= color;\n"
 #endif
diff --git a/panda/src/pgraphnodes/shaderGenerator.cxx b/panda/src/pgraphnodes/shaderGenerator.cxx
index 6712ec7f7b..f6e9c559fd 100644
--- a/panda/src/pgraphnodes/shaderGenerator.cxx
+++ b/panda/src/pgraphnodes/shaderGenerator.cxx
@@ -1218,6 +1218,9 @@ synthesize_shader(const RenderState *rs, const GeomVertexAnimationSpec &anim) {
         text << "\t texcoord" << i << ".xyz -= parallax_offset;\n";
       }
       text << "\t float4 tex" << i << " = tex" << texture_type_as_string(tex._type);
+      if (tex._type == Texture::TT_2d_texture) {
+        text << "proj";
+      }
       text << "(tex_" << i << ", texcoord" << i << ".";
       switch (tex._type) {
       case Texture::TT_cube_map:
@@ -1226,7 +1229,7 @@ synthesize_shader(const RenderState *rs, const GeomVertexAnimationSpec &anim) {
         text << "xyz";
         break;
       case Texture::TT_2d_texture:
-        text << "xy";
+        text << "xyw";
         break;
       case Texture::TT_1d_texture:
         text << "x";