Add basic functionality to draw instances

Allows creation of instances of meshes and drawing all of them with
single draw call. Instances can have their own transformation data
(location, rotation and scale).

graphics/shaders/shader.vert

@@ -6,12 +6,57 @@ layout(binding = 0) uniform UniformBufferObject {
     mat4 proj;
 } ubo;
 
-layout(location = 0) in vec2 inPosition;
+layout(location = 0) in vec3 inPosition;
 layout(location = 1) in vec3 inColor;
 
+layout(location = 2) in vec3 instancePosition;
+layout(location = 3) in vec3 instanceRotation;
+layout(location = 4) in float instanceScale;
+
 layout(location = 0) out vec3 fragColor;
 
-void main() {
-    gl_Position = ubo.proj * ubo.view * ubo.model * vec4(inPosition, 0.0, 1.0);
+void main()
+{
+    mat4 gRotMat;
+    mat3 mx, my, mz;
+
+    // rotate around x
+    float s = sin(instanceRotation.x + 0);
+    float c = cos(instanceRotation.x + 0);
+
+    mx[0] = vec3(1, 0.0, 0.0);
+    mx[1] = vec3(0, c, -s);
+    mx[2] = vec3(0.0, s, c);
+
+    // rotate around y
+    s = sin(instanceRotation.y + 0);
+    c = cos(instanceRotation.y + 0);
+
+    my[0] = vec3(c, 0.0, s);
+    my[1] = vec3(0.0, 1.0, 0.0);
+    my[2] = vec3(-s, 0.0, c);
+
+    // rot around z
+    s = sin(instanceRotation.z + 0);
+    c = cos(instanceRotation.z + 0);
+
+    mz[0] = vec3(c, -s, 0.0);
+    mz[1] = vec3(s, c, 0.0);
+    mz[2] = vec3(0.0, 0.0, 1);
+
+    mat3 rotMat = mz * my * mx;
+
+    s = sin(instanceRotation.y + 0);
+    c = cos(instanceRotation.y + 0);
+    gRotMat[0] = vec4(c, 0.0, s, 0.0);
+    gRotMat[1] = vec4(0.0, 1.0, 0.0, 0.0);
+    gRotMat[2] = vec4(-s, 0.0, c, 0.0);
+    gRotMat[3] = vec4(0.0, 0.0, 0.0, 1.0);
+
+    vec4 locPos = vec4(inPosition.xyz * rotMat, 1.0);
+    vec4 pos = vec4((locPos.xyz * instanceScale) + instancePosition, 1.0);
+
+    gl_Position = ubo.proj * ubo.view * ubo.model * pos;
+
     fragColor = inColor;
 }