vkCmdDispatchIndirect

vkCmdDispatchIndirect is a Vulkan command used to execute a compute shader based on parameters stored in a buffer. Instead of providing the dispatch group counts directly in the command, these counts are read from a VkBuffer. This allows for dynamic dispatch, where the number of workgroups to launch is determined at runtime by previous compute operations or other GPU-side logic.

The command takes a pipeline bind point (always VK_PIPELINE_BIND_POINT_COMPUTE), a compute pipeline handle, and a VkBuffer containing the indirect dispatch parameters. The buffer must be structured to hold three unsigned integer values: x, y, and z dimensions for the dispatch group counts. The offset parameter specifies the byte offset within the buffer where these parameters begin.

Using vkCmdDispatchIndirect is beneficial when the workload size is not known at the time of command buffer recording. For instance, in simulation or particle systems, the number of particles to process or threads to spawn can change dynamically. By writing the dispatch counts to a buffer and then using vkCmdDispatchIndirect, the GPU can efficiently handle these varying workloads without requiring host intervention. This can lead to performance improvements by reducing CPU overhead and enabling more tightly coupled GPU-driven workflows. The buffer used for indirect dispatch must be properly synchronized and contain valid data before the command is executed.