vert

shaders/simple.vert

@@ -3,17 +3,9 @@
 in layout(location=0) vec3 position;
 in layout(location=1) vec4 aColor;
 out vec4 vColor;
-
-mat4 transform;
+uniform mat4 transform;
 
 void main() {
-    transform = mat4(                                                                                                                                            
-        1.0, 0.0, 0.0, 0.0,                                                                                                                                      
-        0.0, 1.0, 0.0, 0.0,                                                                                                                                      
-        0.0, 0.0, 1.0, 0.0,                                                                                                                                      
-        0.0, 0.0, 0.0, 1.0                                                                                                                                       
-    );
-
     gl_Position = transform * vec4(position, 1.0f);
     vColor = aColor;
 }

src/main.rs

@@ -236,6 +236,8 @@ fn main() {
                 .attach_file("./shaders/simple.frag")
                 .link()
         };
+        // get uniform location for the matrix (named `transform` in your vertex shader)
+        let transform_loc = unsafe { simple_shader.get_uniform_location("transform") };
 
         // Used to demonstrate keyboard handling for exercise 2.
         let mut _arbitrary_number = 0.0; // feel free to remove
@@ -298,6 +300,22 @@ fn main() {
 
                 // == // Issue the necessary gl:: commands to draw your scene here
                 simple_shader.activate();
+                // build and send the transform matrix (start from identity)
+                let mut transform: glm::Mat4 = glm::identity();
+                // cycle through each transform parameter (a,b,c,d,e,f) over time
+                let cycle_duration = 2.0;
+                let idx = ((elapsed / cycle_duration).floor() as usize) % 6;
+                let v = elapsed.sin();
+                match idx {
+                    0 => transform[(0,0)] = v, // a
+                    1 => transform[(0,1)] = v, // b
+                    2 => transform[(0,3)] = v, // c
+                    3 => transform[(1,0)] = v, // d
+                    4 => transform[(1,1)] = v, // e
+                    5 => transform[(1,3)] = v, // f
+                    _ => {}
+                }
+                gl::UniformMatrix4fv(transform_loc, 1, gl::FALSE, transform.as_ptr());
                 gl::BindVertexArray(my_vao);
                 gl::DrawElements(
                     gl::TRIANGLES,