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Fractal Renderer is coming together

Fractal Renderer is coming together

I’ve spent the past few months developing a Optix based fractal renderer for my Major project team (as well as a little pipeline), it’s still unfinished but in the end I hope it has at least some of the following features (not all of them are done yet though):

  • Editable scene compiled at runtime into a hit function based on a node graph (the runtime compilation/ptx patching is done, but the node graph still needs work and I’ve fallen back to hard coding the scene description for now). Although the node approach likely won’t be 100% as controllable as writing all the clever scene description stuff by hand (like Shadertoy), it would allow me to quickly patch together a cool looking scene.
  • Passing in data from GUI controls without recompiling the whole hit function, maybe adding in the ability to keyframe values or derive their values per frame from Disney’s SeExpressions.
  • Path Traced Lighting (Done, but looks very odd on my fractal geo, possibly related to me not moving ‘out’ when I hit before firing a shadow ray)
  • Exporting to .exr with handy render passes (Done, OpenImageIO is great for this) – Here’s the output (my normal channel ends up a bit funky, likely related to the same issue that is causing the broken path tracing)

Screenshot from 2016-04-24 22:05:02

Current State

Although there’s still much to be done (outputting animating fractals for instance), this is the type of fractal I can currently render (with a little comp, thanks to the handy render passes):

kyranbulb2

 

Movement Test

The fractal in my major piece has to be moving, specifically some form of tunnel. Given the current state of the renderer, I had to do a separate test just to see how the fractals could move.

Venturing into OptiX – cudaMemcpy breaks everything

I’ve been looking into using Nvidia Optix for my Fractal lookdev tool, as I need realtime feedback while traversing the landscape.

I really like the API so far, it even comes with a Julia example demo in the SDK! I’ve modified it to render the Mandelbulb instead, with little trouble (and with refraction).

12318072_10208255826582355_1853094794_o

However, I needed to read the buffer data to write .exr’s to disk (this is a vital feature, better to make sure it’s viable at the beginning of the project). That shouldn’t be a problem, as I can easily grab the buffer’s device pointer and then cudaMemcpy it over.

All I need to do is include and , no big deal right?

#include <cuda.h>
#include <cuda_runtime.h>
 
#include <optixu/optixpp_namespace.h>
#include <optixu/optixu_math_namespace.h>
 
using namespace optix;
Linking CXX executable ../bin/julia
CMakeFiles/julia.dir/julia.cpp.o: In function `AnimCamera::apply(optix::Handle<optix::ContextObj>)':
/home/tom/src/optix/SDK/julia/julia.cpp:151: undefined reference to `PinholeCamera::PinholeCamera(float3, float3, float3, float, float, PinholeCamera::AspectRatioMode)'
/home/tom/src/optix/SDK/julia/julia.cpp:153: undefined reference to `PinholeCamera::getEyeUVW(float3&, float3&, float3&, float3&)'
collect2: error: ld returned 1 exit status

Oh.

Well maybe it’s because I included them before OptiX.

#include <optixu/optixpp_namespace.h>
#include <optixu/optixu_math_namespace.h>
 
#include <cuda.h>
#include <cuda_runtime.h>
 
using namespace optix;
/usr/local/cuda-7.0/include/cuda_runtime_api.h:257:17: error: ‘cudaError_t’ does not name a type
 extern __host__ cudaError_t CUDARTAPI cudaDeviceReset(void);
                 ^
/usr/local/cuda-7.0/include/cuda_runtime_api.h:274:36: error: ‘cudaError_t’ does not name a type
 extern __host__ __cudart_builtin__ cudaError_t CUDARTAPI cudaDeviceSynchronize(void);
                                    ^
/usr/local/cuda-7.0/include/cuda_runtime_api.h:349:17: error: ‘cudaError_t’ does not name a type
 extern __host__ cudaError_t CUDARTAPI cudaDeviceSetLimit(enum cudaLimit limit, size_t value);
                 ^
 
...
 
/home/tom/src/optix/SDK/julia/julia.cpp:299:95: error: ‘cudaMemcpy’ was not declared in this scope
   cudaMemcpy( (void*)h_ptr, (void*)d_ptr, sizeof(float) * totalPixels, cudaMemcpyDeviceToHost );

Oh.

This is dire, could it be related to the optix namespace somehow?

#include <optixu/optixpp_namespace.h>
#include <optixu/optixu_math_namespace.h>
 
using namespace optix;
 
#include <cuda.h>
#include <cuda_runtime.h>
Linking CXX executable ../bin/julia
[100%] Built target tutorial

Success! For some reason the optix namespace interferes with Cuda, setting it up like I did above somehow fixes that. Maybe this is mentioned in the documentation somewhere but I never found any reference to it.

So if you’re getting undefined references when you need cudaMemcpy in an OptiX project, check out your include order and namespace setup (and don’t forget to add ${CUDA_LIBRARIES} to target_link_libraries in the cmake configuration if it’s not there already).

I haven’t had any other strange problems besides this and so far OptiX seems pretty solid, I hope I’ll have fun with it.

Update

Turns out in this particular instance I was better off using the map() and unmap() functions within the Optix Buffer class instead of cudaMemcpy(), they remove the dependency of including the CUDA headers. However, I would no doubt have run into the same problems using something like the NVRTC headers.