Houdini 21.0 issues with displaying gsplats in Vulkan

[Serzhiv]

Hi!
I installed the new version of GSOPs 2.9.0 for Houdini 21.0 and tried to display a Gaussian through the gaussian_splats_source node. However, I didn't see anything in the viewport in smoothing mode.
In wireframe mode, the Gaussians are present. Apparently, rendering using Vulkan does not work in your version (the same was true in version 20.5). Houdini 21.0 uses Vulkan by default, and I would like to get results in it as well. As I wrote earlier, I compiled my gaussian_splats_source node for version 21.0 from the source code and solved this problem as follows (perhaps incorrectly) by modifying the GR_PrimGsplat::render() method from the GR_GSplat.C file:

void
GR_PrimGsplat::render(
	RE_RenderContext	r,
	GR_RenderMode	    render_mode,
	GR_RenderFlags	    flags,
	GR_DrawParms	    dp)
{
	if(!myWireframeGeo)
	{
		return;
	}

	//TODO, pass in r here, as different viewports could have different render modes.
	GSplatRenderer::getInstance().setRenderingEnabled(render_mode < GR_RENDER_NUM_BEAUTY_MODES);

	bool need_wire =(render_mode == GR_RENDER_WIREFRAME) || (flags & GR_RENDER_FLAG_WIRE_OVER);

	// Only for shaded/beauty
	GSplatRenderer::getInstance().setRenderingEnabled(!need_wire);

    if(need_wire)
    {
		RE_Shader* sh = GsplatShaderManager::getInstance().getShader(GsplatShaderManager::GSPLAT_WIRE_SHADER, r);
		r->pushShader(sh);
		myWireframeGeo->draw(r, RE_GEO_WIRE_IDX);
		r->popShader();
	}
    else
    {
    	GSplatRenderer::getInstance().includeInRenderPass(myRegistryId);

    	if (mySetExplicitCameraPos)
    		GSplatRenderer::getInstance().setExplicitCameraPos(myExplicitCameraPos);

    	GSplatRenderer::getInstance().setSphericalHarmonicsOrder(myShOrder);
    }

	GSplatRenderer::getInstance().includeInRenderPass(myRegistryId);

	if (mySetExplicitCameraPos)
	{
		GSplatRenderer::getInstance().setExplicitCameraPos(myExplicitCameraPos);
	}

	GSplatRenderer::getInstance().setSphericalHarmonicsOrder(myShOrder);
}

There is another problem in the UT_GSplatVectorTypes.h file.
Instead of:
typedef UT_Matrix4T<fpreal16> MyUT_Matrix4H;
I wrote:
typedef UT_Matrix4F MyUT_Matrix4H;

If I am incorrect in my conclusions, then I do not understand why gaussian is not displayed correctly in Vulkan.
Thank you.

[david-rhodes]

Thanks for the report and code @Serzhiv.

I'll take a peek when I get a chance, but first: have you tried disabling viewport lights? If you follow step 4 of the readme, it will change your 3D viewport to OpenGL (this is only required if you want live compositing on Windows--all the other features should work so long as viewport lights are disabled).

[Serzhiv]

Hi @david-rhodes
It's my fault for not paying attention!
I overlooked the fact that all light sources need to be forcibly turned off.
Yes, that's how I got the gsplats display.

But I want to add that this obviously limits visual control when viewing geometry and gsplats together, since there is no lighting.
In the code I sent earlier with my version, there is no need to turn off the lighting.
Of course, there are inconveniences when displaying geometry and gsplats as a sequence of final render overlays (geometry in front, even if it is behind gsplats in depth), but, as I understand it, this cannot be solved yet. Of course, you can try to work around it in one way or another (for example, clipping by depth with a synthetic object based on gsplats points, etc.).

In any case, thanks for the tip! I'll be more careful!

[david-rhodes]

cc @rubendhz

@Serzhiv with the H21 the native viewport (Vulkan) should properly handle depth and compositing with other CG primitive types.

[Serzhiv]

@david-rhodes @rubendhz
That's what I meant

[david-rhodes]

@Serzhiv A fix for viewport lighting will be in the next GSOPs release. Thanks for your support!