From 271a2bb9775dd8a4a6e5a232f27af86ca7ffd83e Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Fri, 7 May 2021 21:17:59 -0400
Subject: model: Improve PBR material handling for glTF models.

---
 data/shaders/pbr-frag.glsl | 73 ++++++++++++++++++++++++++++++++++++----------
 1 file changed, 58 insertions(+), 15 deletions(-)

(limited to 'data/shaders/pbr-frag.glsl')

diff --git a/data/shaders/pbr-frag.glsl b/data/shaders/pbr-frag.glsl
index 813f9a9..ce252ab 100644
--- a/data/shaders/pbr-frag.glsl
+++ b/data/shaders/pbr-frag.glsl
@@ -1,5 +1,23 @@
 // -*- mode: c -*-
 
+struct Material {
+  vec3 baseColorFactor;
+  bool baseColorTextureEnabled;
+  int baseColorTexcoord;
+  float metallicFactor;
+  float roughnessFactor;
+  vec3 normalFactor;
+  bool normalTextureEnabled;
+  int normalTexcoord;
+  vec3 occlusionFactor;
+  bool occlusionTextureEnabled;
+  int occlusionTexcoord;
+  vec3 emissiveFactor;
+  bool emissiveTextureEnabled;
+  int emissiveTexcoord;
+  float alphaCutoff;
+};
+
 #ifdef GLSL120
 attribute vec2 fragTexcoord0;
 attribute vec2 fragTexcoord1
@@ -14,26 +32,51 @@ in vec4 fragColor0;
 out vec4 fragColor;
 #endif
 
-uniform bool textured0;
-uniform bool textured1;
+uniform Material material;
 uniform bool vertexColored;
-uniform vec3 baseColorFactor;
-uniform sampler2D texture0;
-uniform sampler2D texture1;
+uniform sampler2D baseColorTexture;
+uniform sampler2D normalTexture;
+uniform sampler2D occlusionTexture;
+uniform sampler2D emissiveTexture;
+
+vec4 sampleTexture(sampler2D tex, bool enabled, int texcoord, vec3 factor, vec4 defaultColor) {
+  if(enabled && texcoord == 0) {
+    return texture(tex, fragTexcoord0) * vec4(factor, 1.0);
+  } else if(enabled && texcoord == 1) {
+    return texture(tex, fragTexcoord1) * vec4(factor, 1.0);
+  } else {
+    return defaultColor;
+  }
+}
 
-void main (void) {
-  vec4 finalColor = vec4(baseColorFactor, 1.0);
-  // Vertex coloring.
+void main(void) {
+  vec4 finalColor = sampleTexture(baseColorTexture,
+                                  material.baseColorTextureEnabled,
+                                  material.baseColorTexcoord,
+                                  material.baseColorFactor,
+                                  vec4(1.0, 1.0, 1.0, 1.0));
+
+  // Mix in vertex color, if present.
   if(vertexColored) {
     finalColor *= fragColor0;
   }
-  // Texture sampling.
-  if(textured0) {
-    finalColor *= texture(texture0, fragTexcoord0);
-  }
-  if(textured1) {
-    finalColor += texture(texture1, fragTexcoord1);
-  }
+
+  // TODO: Actually apply PBR calculations.
+  finalColor += sampleTexture(normalTexture,
+                              material.normalTextureEnabled,
+                              material.normalTexcoord,
+                              material.normalFactor,
+                              vec4(0.0, 0.0, 0.0, 0.0)) * 0.1;
+  finalColor += sampleTexture(occlusionTexture,
+                              material.occlusionTextureEnabled,
+                              material.occlusionTexcoord,
+                              material.occlusionFactor,
+                              vec4(0.0, 0.0, 0.0, 0.0)) * 0.1;
+  finalColor += sampleTexture(emissiveTexture,
+                              material.emissiveTextureEnabled,
+                              material.emissiveTexcoord,
+                              material.emissiveFactor,
+                              vec4(0.0, 0.0, 0.0, 0.0));
 #ifdef GLSL330
   fragColor = finalColor;
 #else
-- 
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