From f425383178f69591f47ba2a2fb7f90bf57a66db9 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Fri, 7 May 2021 08:34:32 -0400
Subject: model: Add support for vertex colored glTF models.

---
 chickadee/graphics/model.scm | 14 ++++++++------
 chickadee/graphics/pbr.scm   | 36 ++++++++++++++++++++++++++++++------
 2 files changed, 38 insertions(+), 12 deletions(-)

diff --git a/chickadee/graphics/model.scm b/chickadee/graphics/model.scm
index 43f7c3d..58204d6 100644
--- a/chickadee/graphics/model.scm
+++ b/chickadee/graphics/model.scm
@@ -953,15 +953,17 @@
         ("POSITION"
          (attribute-location
           (hash-ref (shader-attributes shader) "position")))
-        ("NORMAL" 1)
-        ("TANGENT" 2)
+        ("NORMAL" 9)
+        ("TANGENT" 10)
         ("TEXCOORD_0"
          (attribute-location
           (hash-ref (shader-attributes shader) "texcoord0")))
-        ("TEXCOORD_1" 4)
-        ("COLOR_0" 5)
-        ("JOINTS_0" 6)
-        ("WEIGHTS_0" 7))))
+        ("TEXCOORD_1" 11)
+        ("COLOR_0"
+         (attribute-location
+          (hash-ref (shader-attributes shader) "color0")))
+        ("JOINTS_0" 12)
+        ("WEIGHTS_0" 13))))
   (define (parse-primitive obj materials accessors)
     (let ((attributes (map (match-lambda
                              ((name . n)
diff --git a/chickadee/graphics/pbr.scm b/chickadee/graphics/pbr.scm
index 5e87135..73f057b 100644
--- a/chickadee/graphics/pbr.scm
+++ b/chickadee/graphics/pbr.scm
@@ -23,6 +23,7 @@
 
 (define-module (chickadee graphics pbr)
   #:use-module (chickadee math vector)
+  #:use-module (chickadee graphics buffer)
   #:use-module (chickadee graphics color)
   #:use-module (chickadee graphics engine)
   #:use-module (chickadee graphics shader)
@@ -93,17 +94,22 @@
 #ifdef GLSL330
 layout (location = 0) in vec3 position;
 layout (location = 1) in vec2 texcoord0;
+layout (location = 2) in vec4 color0;
 #elif defined(GLSL130)
 in vec3 position;
 in vec2 texcoord0;
+in vec4 color0;
 #elif defined(GLSL120)
 attribute vec3 position;
 attribute vec2 texcoord0;
+attribute vec4 color0;
 #endif
 #ifdef GLSL120
 varying vec2 fragTex;
+varying vec4 fragVertColor;
 #else
 out vec2 fragTex;
+out vec4 fragVertColor;
 #endif
 uniform mat4 model;
 uniform mat4 view;
@@ -111,37 +117,55 @@ uniform mat4 projection;
 
 void main(void) {
   fragTex = texcoord0;
+  fragVertColor = color0;
   gl_Position = projection * view * model * vec4(position.xyz, 1.0);
 }
 "
    "
 #ifdef GLSL120
 attribute vec2 fragTex;
+attribute vec4 fragVertColor;
 #else
 in vec2 fragTex;
+in vec4 fragVertColor;
 #endif
 #ifdef GLSL330
 out vec4 fragColor;
 #endif
+uniform bool textured;
+uniform bool vertexColored;
 uniform vec3 baseColorFactor;
 uniform sampler2D baseColorTexture;
 
 void main (void) {
+  vec4 finalColor = vec4(baseColorFactor, 1.0);
+  if(vertexColored) {
+    finalColor *= fragVertColor;
+  }
+  if(textured) {
+    finalColor *= texture(baseColorTexture, fragTex);
+  }
 #ifdef GLSL330
-  fragColor = texture(baseColorTexture, fragTex) *
-    vec4(baseColorFactor, 1.0);
+  fragColor = finalColor;
 #else
-  gl_FragColor = texture2D(baseColorTexture, fragTex) *
-    vec4(baseColorFactor, 1.0);
+  gl_FragColor = finalColor;
 #endif
 }
 "))
 
 (define (shader-apply/pbr vertex-array material model-matrix view-matrix)
-  (let ((shader (graphics-variable-ref pbr-shader)))
-    (with-graphics-state ((g:texture-0 (pbr-material-base-color-texture material)))
+  (let* ((shader (graphics-variable-ref pbr-shader))
+         (base-color-texture (pbr-material-base-color-texture material))
+         (vattrs (vertex-array-attributes vertex-array))
+         (sattrs (shader-attributes shader)))
+    (with-graphics-state ((g:texture-0 base-color-texture))
       (shader-apply shader vertex-array
                     #:model model-matrix
                     #:view view-matrix
                     #:projection (current-projection)
+                    #:textured (not (eq? base-color-texture null-texture))
+                    #:vertex-colored (buffer-view?
+                                      (assv-ref vattrs
+                                                (attribute-location
+                                                 (hash-ref sattrs "color0"))))
                     #:base-color-factor (pbr-material-base-color-factor material)))))
-- 
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