CODEWITHSUNDEEP
c++performancegraphics2dvulkan
Jordie
Jordie

Reputation: 11

How many draw calls is acceptable in vulkan?

Ive been working on a vulkan renderer and am having a bit of a pickle. Currently I am using vulkan to render 2d sprites, and just imported a whole map to draw. The map is 40x40 with 1600 tiles. I cannot instance/batch these as there are moving objects in the scene and I may need to interject draw calls in between ( Some objects need to be rendered in front of others ). However, when I render these 1600 sprites individually my cpu CHUGS and it takes ~20ms to accomplish JUST the sprites. This happens in a separate thread and does the following:

Start command buffer & render pass 
 For every sprite to draw
   Set up translation matrix.
   Fetch the material if its not cached
   If this command buffer is not bound to the pipeline bind it.
   Bind the descriptor set given by the material if not already bound.
   Push translation matrix to pipeline using push constant.
   Draw.
End command buffer & render pass & submit.

My question I guess is, is 1600 too much? Should I try and find ways to batch this? Would it make more sense to just spend these clock cycles building a big buffer on the gpu and only draw once? I figured this was less efficient since I only really submit once for all commands given.

Upvotes: 1

Views: 2216

Answers (1)

MarvinWS
MarvinWS

Reputation: 41

Yes, 1600 draw calls for this type of application is too many. It sounds like you could possibly use a single vkCmdDrawIndexedIndirect().

You would just need to create SSBOs for your per sprite matrices and texture samplers to index into each draw using gl_DrawIDARB in the shaders (don't forget to enable VK_KHR_SHADER_DRAW_PARAMETERS_EXTENSION_NAME).

Your CPU-side pre-draw preparation per frame would consist of setting the correct vertex/index buffer offsets within the VkDrawIndexedIndirectCommand structure, as well as setting up any required texture loads and populating your descriptors.

If draw order is a consideration for you, your application could track depth per sprite and then make sure they're set up for draw in the correct order.

Upvotes: 2

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