graphics: Add basic image based ambient lighting.

4 files changed, 36 insertions, 25 deletions

diff --git a/chickadee/graphics/mesh.scm b/chickadee/graphics/mesh.scm
index ab7ad45..44c670e 100644
--- a/chickadee/graphics/mesh.scm
+++ b/chickadee/graphics/mesh.scm
@@ -33,6 +33,7 @@
   #:use-module (chickadee graphics light)
   #:use-module (chickadee graphics polygon)
   #:use-module (chickadee graphics shader)
+  #:use-module (chickadee graphics skybox)
   #:use-module (chickadee graphics stencil)
   #:use-module (chickadee graphics texture)
   #:use-module (chickadee utils)
@@ -123,24 +124,26 @@
 (define %camera-position (vec3 0.0 0.0 0.0))
 
 (define (material-apply material vertex-array model-matrix view-matrix
-                        camera-position ambient-light light-vector)
+                        camera-position skybox light-vector)
   (with-graphics-state ((g:blend-mode (material-blend-mode material))
                         (g:cull-face-mode (material-cull-face-mode material))
                         (g:depth-test (material-depth-test material))
                         (g:multisample? (material-multisample? material))
                         (g:polygon-mode (material-polygon-mode material))
                         (g:stencil-test (material-stencil-test material))
-                        (g:texture-0 (material-texture-0 material))
-                        (g:texture-1 (material-texture-1 material))
-                        (g:texture-2 (material-texture-2 material))
-                        (g:texture-3 (material-texture-3 material))
-                        (g:texture-4 (material-texture-4 material)))
+                        (g:texture-0 (if skybox
+                                         (skybox-cube-map skybox)
+                                         null-texture))
+                        (g:texture-1 (material-texture-0 material))
+                        (g:texture-2 (material-texture-1 material))
+                        (g:texture-3 (material-texture-2 material))
+                        (g:texture-4 (material-texture-3 material))
+                        (g:texture-5 (material-texture-4 material)))
     (shader-apply (material-shader material) vertex-array
                   #:model model-matrix
                   #:view view-matrix
                   #:projection (current-projection)
                   #:camera-position camera-position
-                  #:ambient-light ambient-light
                   #:lights light-vector
                   #:material (material-properties material))))
 
@@ -159,13 +162,13 @@
   (material primitive-material))
 
 (define (draw-primitive primitive model-matrix view-matrix camera-position
-                        ambient-light light-vector)
+                        skybox light-vector)
   (material-apply (primitive-material primitive)
                   (primitive-vertex-array primitive)
                   model-matrix
                   view-matrix
                   camera-position
-                  ambient-light
+                  skybox
                   light-vector))
 
 
@@ -190,7 +193,7 @@
 (define* (draw-mesh mesh #:key (model-matrix %identity-matrix)
                     (view-matrix %identity-matrix)
                     (camera-position %origin)
-                    (ambient-light black)
+                    skybox
                     (lights '()))
   ;; Populate light vector to pass on to shader.
   (let ((light-vector (mesh-light-vector mesh)))
@@ -206,7 +209,7 @@
            (loop (+ i 1) rest)))))
     (for-each (lambda (primitive)
                 (draw-primitive primitive model-matrix view-matrix camera-position
-                                ambient-light light-vector))
+                                skybox light-vector))
               (mesh-primitives mesh))))
 
 
diff --git a/chickadee/graphics/model.scm b/chickadee/graphics/model.scm
index 8b7cbda..839ddd1 100644
--- a/chickadee/graphics/model.scm
+++ b/chickadee/graphics/model.scm
@@ -114,11 +114,10 @@
                           (children '()))
   (%make-model-node name mesh matrix world-matrix children))
 
-(define (draw-model-node node state view-matrix camera-position ambient-light
-                         lights)
+(define (draw-model-node node state view-matrix camera-position skybox lights)
   (for-each (lambda (child)
               (draw-model-node child state view-matrix camera-position
-                               ambient-light lights))
+                               skybox lights))
             (model-node-children node))
   (let ((mesh (model-node-mesh node)))
     (when mesh
@@ -128,7 +127,7 @@
                  #:model-matrix (render-state-world-model-matrix state)
                  #:view-matrix view-matrix
                  #:camera-position camera-position
-                 #:ambient-light ambient-light
+                 #:skybox skybox
                  #:lights lights))))
 
 
@@ -152,7 +151,7 @@
 (define %depth-test (make-depth-test))
 
 (define* (draw-model model model-matrix view-matrix camera-position #:key
-                     (ambient-light black)
+                     skybox
                      (lights '()))
   (with-graphics-state ((g:depth-test %depth-test)
                         (g:multisample? #t))
@@ -161,7 +160,7 @@
       (render-state-model-matrix-mult! state model-matrix)
       ;; TODO: Support drawing non-default scenes.
       (draw-model-node (model-default-scene model) state view-matrix
-                       camera-position ambient-light lights))))
+                       camera-position skybox lights))))
 
 
 ;;;
diff --git a/data/shaders/pbr-frag.glsl b/data/shaders/pbr-frag.glsl
index c474981..fff725a 100644
--- a/data/shaders/pbr-frag.glsl
+++ b/data/shaders/pbr-frag.glsl
@@ -47,9 +47,9 @@ out vec4 fragColor;
 
 uniform Material material;
 uniform Light lights[MAX_LIGHTS];
-uniform vec4 ambientLight;
 uniform bool vertexColored;
 uniform vec3 cameraPosition;
+uniform samplerCube skybox;
 uniform sampler2D baseColorTexture;
 uniform sampler2D metallicRoughnessTexture;
 uniform sampler2D normalTexture;
@@ -244,6 +244,7 @@ void main(void) {
   float metallic = materialMetallic();
   float roughness = materialRoughness();
   vec3 normal = materialNormal();
+  vec3 reflection = reflect(-viewDirection, normal);
   // The "raw" albedo has an alpha channel which we need to preserve
   // so that we can apply the desired alpha blending method at the
   // end, but it is completely ignored for lighting calculations.
@@ -356,11 +357,14 @@ void main(void) {
   // The emissive texture says which fragments emit light.  We simply
   // add this light value to the color accumulator.
   color += materialEmissive();
-  // Apply simple ambient lighting.  The affect of the ambient light
-  // is dampened by the ambient occlusion factor.
+  // Apply image based ambient lighting.  The affect of the ambient
+  // light is dampened by the ambient occlusion factor.
   //
-  // TODO: Use image based lighting.
-  color += ambientLight.rgb * albedo * ambientOcclusion;
+  // TODO: Use fancy PBR equations instead of these basic ones.
+  float fresnel = pow(1.0 - clamp(dot(viewDirection, normal), 0.0, 1.0), 5);
+  vec3 ambientDiffuse = textureCube(skybox, normal).rgb;
+  vec3 ambientSpecular = textureLod(skybox, reflection, roughness * 7.0).rgb;
+  color += (ambientDiffuse * albedo + ambientSpecular * fresnel) * ambientOcclusion;
   // Apply Reinhard tone mapping to convert our high dynamic range
   // color value to low dynamic range.  All of the lighting
   // calculations stacked on top of each other is likely to create
diff --git a/data/shaders/phong-frag.glsl b/data/shaders/phong-frag.glsl
index 0beb75b..9c86c83 100644
--- a/data/shaders/phong-frag.glsl
+++ b/data/shaders/phong-frag.glsl
@@ -32,6 +32,7 @@ in vec2 fragTex;
 out vec4 fragColor;
 #endif
 
+uniform samplerCube skybox;
 uniform sampler2D ambientMap;
 uniform sampler2D diffuseMap;
 uniform sampler2D specularMap;
@@ -39,7 +40,6 @@ uniform sampler2D normalMap;
 uniform Material material;
 uniform Light lights[MAX_LIGHTS];
 uniform vec3 cameraPosition;
-uniform vec4 ambientLight;
 
 const float GAMMA = 2.2;
 
@@ -135,6 +135,7 @@ void main() {
   vec3 diffuseColor = materialDiffuse();
   vec3 specularColor = materialSpecular();
   vec3 normal = materialNormal();
+  vec3 reflection = reflect(-viewDir, normal);
   vec3 color = vec3(0.0);
 
   // Apply direct lighting.
@@ -155,8 +156,12 @@ void main() {
     color += diffuseLight * diffuseColor + specularLight * specularColor;
   }
 
-  // Apply ambient lighting.
-  vec3 ambientColor = diffuseColor * ambientLight.rgb * ambientOcclusion;
+  // Apply image based ambient lighting.
+  float fresnel = pow(1.0 - clamp(dot(viewDir, normal), 0.0, 1.0), 5);
+  float roughness = 1.0 - (material.shininess / 1000.0);
+  vec3 ambientDiffuse = textureCube(skybox, normal).rgb * diffuseColor;
+  vec3 ambientSpecular = textureLod(skybox, reflection, roughness * 7.0).rgb * fresnel;
+  vec3 ambientColor = (ambientDiffuse + ambientSpecular) * ambientOcclusion;
   color += ambientColor;
 
   // Apply gamma correction and HDR tone mapping to get the final