render: Bypass texture rendering when a model uses the null texture.

* data/shaders/default-fragment.glsl (use_texture): New uniform.
  (main): Skip texture rendering when 'use_texture' is false.
* sly/render/model.scm (draw-model): Set 'use_texture' uniform before
  rendering.
* sly/render/shader.scm (load-default-shader): Register 'use_texture'
  uniform.

1 files changed, 5 insertions, 0 deletions

diff --git a/data/shaders/default-fragment.glsl b/data/shaders/default-fragment.glsl
index 21bb756..a447a79 100644
--- a/data/shaders/default-fragment.glsl
+++ b/data/shaders/default-fragment.glsl
@@ -3,7 +3,12 @@
 in vec2 frag_tex;
 uniform vec4 color;
 uniform sampler2D color_texture;
+uniform bool use_texture;
 
 void main (void) {
+  if(use_texture) {
     gl_FragColor = texture2D(color_texture, frag_tex) * color;
+  } else {
+    gl_FragColor = color;
+  }
 }