Render hooks

[Josh]

@klepto2 @SpiderPig

I am adding rendering hooks into the engine that will be called in the rendering thread. The two hooks I have planned are:

 

• HOOKID_COMPUTE - called once per render before drawing begins
• HOOKID_DRAWCAMERA - called once per pass for each camera or shadow render

 

Hooks can be added to an object with this mechanism:

void Object::AddHook(const HookID id, void (*hook)(std::shared_ptr<Object> source, std::shared_ptr<Object> extra), std::shared_ptr<Object> extra = NULL);

They will pass an OpenGLRenderer object as the source argument of the function callback.

void CustomRenderHook(shared_ptr<Object> o, shared_ptr<Object> extra)
{
	auto renderer = o->As<OpenGLRenderer>();
	
	// Start drawing!
  
}

The structure contains this information. Is there anything else missing that you need?

struct OpenGLRenderer : public Object
{
	HGLRC context;
	GLuint framebuffer;
 	iVec4 viewport;
	std::array<GLuint, MAX_STORAGE_BUFFERS> storagebuffers;
	uint32_t cameraid;
	Mat4 cameramatrix;
	std::array<Mat4, 6> projectioncameramatrix;
	OpenGLRenderPass pass;
};

I am trying to stick with the raw OpenGL data and avoid use of the internal API classes as much as possible.

The pass value can be any of the following:

• RENDERPASS_DEPTH
• RENDERPASS_SOLID
• RENDERPASS_SHADOW
• RENDERPASS_TRANSPARENCY
• RENDERPASS_REFRACTION

If the depth prepass is disabled, then the solid pass will indicate RENDERPASS_SOLID | RENDERPASS_DEPTH.

[Josh]

This is available now in 0.9.8 beta.

[klepto2]

Very nice, thank you. Will take a closer look into this soon

I have 2 more requests:

1. Maybe we need a HOOKID_COMPUTE_AT_START and a HOOKID_COMPUTE_AT_END
   1. This is because some computations may rely on data produced after the whole rendering is done.
2. It would be nice to have also access to camera frustumn (if possible) 
   1. Some geometric code might need this (like my quadtree implemntation)

[klepto2]

also it would be nice (if possible at all) to have a cancel option. This way it could be possible to have something like this:

 

void DepthOnlyRenderHook(shared_ptr<Object> o, shared_ptr<Object> extra)
{
	auto renderer = o->As<OpenGLRenderer>();
	auto camera = extra->As<Camera>();
  
  	//what is the cameraid actual?
  	if(camera->GetId() == renderer->cameraid && (pass & RENDERPASS_DEPTH) == 0)
    {
      // disable all other passes and just draw the depth pass
      // might be much cheaper for much scenarios where later computations are just dependend on the depth.
      renderer.cancel = true;
    }
}

 

[Josh]

7 hours ago, klepto2 said:

• Maybe we need a HOOKID_COMPUTE_AT_START and a HOOKID_COMPUTE_AT_END
  1. This is because some computations may rely on data produced after the whole rendering is done.
• It would be nice to have also access to camera frustumn (if possible) 
  1. Some geometric code might need this (like my quadtree implemntation)

Ah, okay, so like per-camera compute.

 

[Josh]

I will add this member in the next build:

std::array<Plane, 6> camerafrustum;