glMultiDrawElementsIndirect error?

OpenGL OpenGL: Advanced Coding
1

My indirect draw command structure is declared like this:

typedef struct {
	uint32_t count;
	uint32_t instanceCount;
	uint32_t firstIndex;
	int32_t baseVertex;
	uint32_t baseInstance;
} DrawElementsIndirectCommand;

This code works as expected:

for (const auto& command : vislist->drawcommands)
{
	glDrawElementsInstancedBaseVertexBaseInstance(GL_TRIANGLES, command.count, GL_UNSIGNED_INT, (void*)(command.firstIndex * 4), command.instanceCount, command.baseVertex, command.baseInstance);
}

This code produces GL_ERROR_INVALID_OPERATION. The stride value is 20.

Assert(glGetInteger(GL_DRAW_INDIRECT_BUFFER_BINDING) == 0);
Assert(glGetInteger(GL_ELEMENT_ARRAY_BUFFER_BINDING) != 0);
int stride = sizeof(vislist->drawcommands[0]);
Assert(stride == 20);
glMultiDrawElementsIndirect(GL_TRIANGLES, GL_UNSIGNED_INT, vislist->drawcommands.data(), vislist->drawcommands.size(), stride);

The number of draw commands is one. The drawcommands value is declared like this:

std::vector<DrawElementsIndirectCommand> drawcommands;

Any ideas what is wrong?

2

There’s your problem. Core OpenGL does not allow you to use CPU memory for indirect rendering. You have to put the indirect commands in buffer objects.

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