[osg-users] Nvidia RTX

[Lionel Lagarde]

The RTX examples I found (like 
https://iorange.github.io/p01/HappyTriangle.html) use a VK command 
(similar to a compute dispatch) to trigger the ray tracing:

|void vkCmdTraceRaysNVX(VkCommandBuffer commandBuffer, VkBuffer 
raygenShaderBindingTableBuffer, VkDeviceSize raygenShaderBindingOffset, 
VkBuffer missShaderBindingTableBuffer, VkDeviceSize 
missShaderBindingOffset, VkDeviceSize missShaderBindingStride, VkBuffer 
hitShaderBindingTableBuffer, VkDeviceSize hitShaderBindingOffset, 
VkDeviceSize hitShaderBindingStride, uint32_t width, uint32_t height); |

This function posts the ray tracing command to a VK command queue. 
Finally, the main ray tracing shader "stores" the ray tracing result in 
an image using imageStore.

I don't know about mixing an OpenGL context and the VK counterpart 
(device, physical device, command queue, images...). It is maybe 
possible but like the CUDA /GL interoperability, it may require 
expansive synchronization mechanisms.


On 21/02/2019 15:19, Chris Hanson wrote:
> So, you'd need a shared GL/Vk context in order to Vk load the data and 
> then GL trace it, if I understand correctly?
>
> We could probably bring VSG into play to load the data. I think 
> there's enough working code there already to do so. Or, really, we 
> could just us what VSG has already and compose and execute the RTX 
> commands without OSG, but copying already-composed scene data over 
> from the OSG side.
>
> On Thu, Feb 21, 2019 at 3:15 PM Lionel Lagarde 
> <lionel.lagarde at oktal-se.fr <mailto:lionel.lagarde at oktal-se.fr>> wrote:
>
>     Hi,
>
>     It is a GLSL extension, the ray tracing functions use some input
>     data (like the acceleration structure) that can only be
>     constructed and uploaded using the vk API.
>
>
>     On 21/02/2019 13:34, Chris Hanson wrote:
>>     One of my guys pointed out this recent addition:
>>
>>     https://github.com/KhronosGroup/GLSL/blob/master/extensions/nv/GLSL_NV_ray_tracing.txt
>>
>>
>>     On Wed, Feb 20, 2019 at 9:47 PM Chris Hanson
>>     <xenon at alphapixel.com <mailto:xenon at alphapixel.com>> wrote:
>>
>>
>>         Well, I was wondering if there was an OpenGL RTX API
>>         anywhere, but it doesn't seem there is.
>>
>>         Vulkan would appear to be the way to go for the future, but
>>         since that's not ready for the oven yet (don't even have all
>>         the mise en place), it might be we just have to make a
>>         utility library to shovel OSG data into OptiX and let it do
>>         the work for now. There's always going to have to be some
>>         kind of bridge from OSG to either Vulkan or something else if
>>         no OpenGL support extension ever appears.
>>
>>
>>
>>     -- 
>>     Chris 'Xenon' Hanson, omo sanza lettere. Xenon at AlphaPixel.com
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> -- 
> Chris 'Xenon' Hanson, omo sanza lettere. Xenon at AlphaPixel.com 
> http://www.alphapixel.com/
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