draw multiple cubes and make every side have a different colour

src/main.c

@@ -228,47 +228,87 @@ void init(void) {
 
 GLfloat currentHue = 0.0f;
 
+void drawCube(vec3 position, mat4 initialModelMatrix, mat4 viewMatrix) {
+	mat4 modelMatrix;
+	mat4 modelViewMatrix;
+
+	mat4Translate(modelMatrix, initialModelMatrix, position);
+
+	// combine model and view matrix to model-view matrix
+	mat4Multiply(modelViewMatrix, viewMatrix, modelMatrix);
+
+	// send modelView and projection matrix to shader
+	GLuint modelViewLocation = glGetUniformLocation(program, "uModelView");
+	glUniformMatrix4fv(modelViewLocation, 1, GL_FALSE, modelViewMatrix);
+
+	// draw cube
+	glBindVertexArray(vertexArrayObject);
+	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffer);
+	glDrawElements(GL_TRIANGLES, 48, GL_UNSIGNED_INT, 0);
+}
+
 void draw(void) {
 	updateStatusDisplay();
 
+	// counter for animation
 	currentHue += 0.0005f;
 	if (currentHue > 1.0) currentHue = 0.0f;
 
+	// clear colour and depth buffer
 	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+
+	// select program
 	glUseProgram(program);
 
-	mat4 transformMatrix;
-	vec3 scale = {0.2f, 0.2f, 0.2f};
-	vec3 position = {0.0f, 0.0f, -1.0f};
-	mat4Identity(transformMatrix);
-	mat4Scale(transformMatrix, transformMatrix, scale);
-	
-	mat4RotateZ(transformMatrix, transformMatrix, currentHue * PI * 2);
-	mat4RotateY(transformMatrix, transformMatrix, currentHue * PI * 2);
-
-	mat4Translate(transformMatrix, transformMatrix, position);
-
+	// build view matrix
 	mat4 viewMatrix;
-	mat4Identity(viewMatrix);
-	vec3 cameraPos = {0.0f, 0.0f, 0.0f};
+
+	// mat4Identity(viewMatrix);
+	vec3 cameraPos = {0.0f, 0.0f, 2.0f};
 	vec3 cameraLookAt = {0.0f, 0.0f, -1.0f};
 	vec3 cameraUp = {0.0f, 1.0f, 0.0f};
 	mat4BuildLookAt(viewMatrix, cameraPos, cameraLookAt, cameraUp);
 
-	mat4 modelViewMatrix;
-	mat4Multiply(modelViewMatrix, viewMatrix, transformMatrix);
-
-
-	GLuint modelViewLocation = glGetUniformLocation(program, "uModelView");
-	glUniformMatrix4fv(modelViewLocation, 1, GL_FALSE, modelViewMatrix);
-
 	GLuint projectionLocation = glGetUniformLocation(program, "uProjection");
 	glUniformMatrix4fv(projectionLocation, 1, GL_FALSE, projectionMatrix);
 
 
-	glBindVertexArray(vertexArrayObject);
-	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffer);
-	glDrawElements(GL_TRIANGLES, 48, GL_UNSIGNED_INT, 0);
+	// build model Matrix
+	mat4 modelMatrix;
+	vec3 scale;
+	vec3 position;
+	mat4 scaledMatrix;
+
+	mat4Identity(scaledMatrix);
+
+	vec3Set(scale, 0.2f, 0.2f, 0.2f);
+	mat4Scale(scaledMatrix, scaledMatrix, scale);
+	
+
+	// draw cubes
+	// cube 1
+	vec3Set(position, -1.0f, 0.0f, 0.0f);
+
+	mat4RotateZ(modelMatrix, scaledMatrix, currentHue * PI * 4);
+	mat4RotateY(modelMatrix, modelMatrix, currentHue * PI * 2);
+
+	drawCube(position, modelMatrix, viewMatrix);
+
+	// cube 2
+	vec3Set(position, 0.0f, 0.0f, 0.0f);
+
+	mat4RotateY(modelMatrix, scaledMatrix, currentHue * PI * 4);
+	mat4RotateX(modelMatrix, modelMatrix, currentHue * PI * 2);
+
+	drawCube(position, modelMatrix, viewMatrix);
+
+	// cube 3
+	vec3Set(position, 1.0f, 0.0f, 0.0f);
+
+	mat4RotateX(modelMatrix, scaledMatrix, currentHue * PI * 4);
+	mat4RotateZ(modelMatrix, modelMatrix, currentHue * PI * 2);
+
+	drawCube(position, modelMatrix, viewMatrix);
 }
 
 void framebuffer_size_callback(GLFWwindow* window, int width, int height) {

src/shaders/fragment.glsl

@@ -1,5 +1,15 @@
 #version 330 core
-in vec3 vertexColor;
+vec3 colors[6] = vec3[6](
+	vec3(1.0, 0.5, 0.5),
+	vec3(0.5, 1.0, 0.5),
+	vec3(0.5, 0.5, 1.0),
+	vec3(1.0, 1.0, 0.5),
+	vec3(1.0, 0.5, 1.0),
+	vec3(0.5, 1.0, 1.0) 
+);
+
 void main() {
-	gl_FragColor = vec4(vertexColor, 1.0);
+	// hacky solution to give each side a different colour
+	int side = gl_PrimitiveID / 2;
+	gl_FragColor = vec4(colors[side], 1.0);
 }

src/shaders/vertex.glsl

@@ -3,9 +3,6 @@ layout (location = 0) in vec3 aPosition;
 uniform mat4 uModelView;
 uniform mat4 uProjection;
 
-out vec3 vertexColor;
-
 void main() {
-	vertexColor = (aPosition + vec3(1)) / 2;
 	gl_Position = uProjection * uModelView * vec4(aPosition, 1.0);
 }