DEVLOG 19 - Colors!

 
Hi Stardance!
I’ve made some progress and finally drew something on the screen!
 
Improvements on the Swapchain Pass
I’ve improved the Render Graph a bit by cleaning up old methods and making all the improvements discussed in the last devlog, such as improving the rendering code for the swapchain. Normally, you would set the 2D texture to display on the screen using the RenderGraph::SetPresentTexture(); In reality, this texture isn’t displayed directly on the screen but is first sampled and copied to the swapchain, so the Render Graph adds a hidden pass for this. When this texture hasn’t been assigned to any texture, the swapchain will be colored with the clear value set to black and sent to the screen.
 
Push Constants Supported
I’ve added the ability to use Vulkan Push Constants. Push Constants are data packets that can be sent to the GPU in parallel with the drawing command. Their size is very limited, 128 bytes, but their transfer speed is extremely fast. A hardware limitation is that the offset and size parameters must be multiples of four, so I used a struct called Words32 to dictate the 32-bit size and offset, not the 8-bit one. Furthermore, internally, the engine checks the state of the previous push constant for each push constant update, so as not to make unnecessary updates and to register the push constant command only when necessary, and only partially for the relevant bytes.
 
Shaders Improvements
I improved the shader code a bit by reducing the arguments needed to create a shader, and I also unified the layout; all shaders use the same VkPipelineLayout.
 
The Problem and The Solution
When I was writing the shaders to get these things on screen, I ran into errors telling me I was assigning a buffer descriptor to Descriptor Set 0 with binding 0, even though they’re actually textures. However, in the shader, I wasn’t requesting any of this, since the vertex data was written directly into the shader. After some research, I discovered that Slang shaders were creating bindings for these arrays outside the shader. To fix this, I simply moved the arrays into the vertex shader function, marking them with const.
 
And note that all these images/videos use the swapchain pass, so this was all just a test. Now I’ll have to try declaring a real pass with Render Graph and try to draw something, hoping everything works correctly :/