Rotate targetting reticule to mob. Add pivot point

Notion of pivot point now for rotating, i.e. the anchor point at which
rotations are applied. Rotating the reticule is done by using inverse
trigonometry, namely atan2f.

src/Renderer.c

@@ -87,20 +87,16 @@ createDefaultTexQuad(Renderer *renderer, RenderTex renderTex)
 	return result;
 }
 
-INTERNAL void renderObject(Renderer *renderer, v2 pos, v2 size, f32 rotate,
-                           v4 color, Texture *tex)
+INTERNAL void renderObject(Renderer *renderer, v2 pos, v2 size, v2 pivotPoint,
+                           f32 rotate, v4 color, Texture *tex)
 {
 	mat4 transMatrix  = mat4_translate(pos.x, pos.y, 0.0f);
-	// NOTE(doyle): Rotate from the center of the object, not its' origin (i.e.
-	// top left)
-	mat4 rotateMatrix = mat4_translate((size.x * 0.5f), (size.y * 0.5f), 0.0f);
+	// NOTE(doyle): Rotate from pivot point of the object, (0, 0) is top left
+	mat4 rotateMatrix = mat4_translate(pivotPoint.x, pivotPoint.y, 0.0f);
 	rotateMatrix = mat4_mul(rotateMatrix, mat4_rotate(rotate, 0.0f, 0.0f, 1.0f));
-	rotateMatrix = mat4_mul(rotateMatrix, mat4_translate((size.x * -0.5f), (size.y * -0.5f), 0.0f));
+	rotateMatrix = mat4_mul(rotateMatrix, mat4_translate(-pivotPoint.x, -pivotPoint.y, 0.0f));
 
 	// NOTE(doyle): We draw everything as a unit square in OGL. Scale it to size
-	// TODO(doyle): We should have a notion of hitbox size and texture size
-	// we're going to render so we can draw textures that may be bigger than the
-	// entity, (slightly) but keep a consistent bounding box
 	mat4 scaleMatrix = mat4_scale(size.x, size.y, 1.0f);
 	mat4 model = mat4_mul(transMatrix, mat4_mul(rotateMatrix, scaleMatrix));
 
@@ -140,7 +136,7 @@ INTERNAL void renderObject(Renderer *renderer, v2 pos, v2 size, f32 rotate,
 }
 
 void renderer_rect(Renderer *const renderer, v4 cameraBounds, v2 pos, v2 size,
-                   f32 rotate, RenderTex renderTex, v4 color)
+                   v2 pivotPoint, f32 rotate, RenderTex renderTex, v4 color)
 {
 	RenderQuad quad = createDefaultTexQuad(renderer, renderTex);
 	updateBufferObject(renderer, &quad, 1);
@@ -148,13 +144,14 @@ void renderer_rect(Renderer *const renderer, v4 cameraBounds, v2 pos, v2 size,
 	// NOTE(doyle): Get the origin of cameraBounds in world space, bottom left
 	v2 offsetFromCamOrigin  = V2(cameraBounds.x, cameraBounds.w);
 	v2 rectRelativeToCamera = v2_sub(pos, offsetFromCamOrigin);
-	renderObject(renderer, rectRelativeToCamera, size, rotate, color,
-	             renderTex.tex);
+	renderObject(renderer, rectRelativeToCamera, size, pivotPoint, rotate,
+	             color, renderTex.tex);
 }
 
 void renderer_string(Renderer *const renderer, MemoryArena *arena,
                      v4 cameraBounds, Font *const font,
-                     const char *const string, v2 pos, f32 rotate, v4 color)
+                     const char *const string, v2 pos, v2 pivotPoint,
+                     f32 rotate, v4 color)
 {
 	i32 strLen       = common_strlen(string);
 	// TODO(doyle): Scale, not too important .. but rudimentary infrastructure
@@ -208,14 +205,14 @@ void renderer_string(Renderer *const renderer, MemoryArena *arena,
 		// relative to the window size, hence we also render at the origin since
 		// we're rendering a window sized buffer
 		updateBufferObject(renderer, stringQuads, quadIndex);
-		renderObject(renderer, V2(0.0f, 0.0f), renderer->size, rotate, color,
-		                font->tex);
+		renderObject(renderer, V2(0.0f, 0.0f), renderer->size, pivotPoint,
+		             rotate, color, font->tex);
 		PLATFORM_MEM_FREE(arena, stringQuads, strLen * sizeof(RenderQuad));
 	}
 }
 
 void renderer_entity(Renderer *renderer, v4 cameraBounds, Entity *entity,
-                     f32 rotate, v4 color)
+                     v2 pivotPoint, f32 rotate, v4 color)
 {
 	// TODO(doyle): Batch into render groups
 
@@ -247,6 +244,6 @@ void renderer_entity(Renderer *renderer, v4 cameraBounds, Entity *entity,
 		v2 entityRelativeToCamera = v2_sub(entity->pos, offsetFromCamOrigin);
 
 		renderObject(renderer, entityRelativeToCamera, entity->renderSize,
-		             rotate, color, entity->tex);
+		             pivotPoint, rotate, color, entity->tex);
 	}
 }