This sample creates a 3D texture and fill the image data with a compute shader, or from the host with the CPU.
The image generation follows Perlin noise, and octave, power and frequency were added to add perturbation to the noise function. The creation of the data for the image can be found in perlin.comp, and the software version of it, is called fillPerlinImage.
The image that is generated is always of power-of-two size, which means the image will be a cube of 2^level. By default, it is 64x64x64.
A cube is rendered, and in the fragment shader, the intersection P1 and P2 is found, a ray-marching will be done between those points until it goes over a threshold value. Once the intersection point is found, the gradient is calculated to find the normal at the surface. This normal is used for shading. See raster.frag.glsl for the shading code.
Resources are bound bindless through VK_EXT_descriptor_heap via nvvk::DescriptorHeap, instead of descriptor sets. Shaders are created as shader objects with VK_SHADER_CREATE_DESCRIPTOR_HEAP_BIT_EXT, and push data is sent with vkCmdPushDataEXT.
This sample is a good example of a mixed resource heap: the 3D texture image + its sampler live in the image/sampler regions, while the per-frame uniform buffer lives in the buffer region. Because a resource heap packs images first and buffers after, buffer slots are addressed from bufferShaderIndexBase() (threaded to the shader through a push-constant field), not from raw index 0 — a detail that matters whenever a single heap mixes images and buffers.
See the descriptor_heap sample for the concept in depth.
The first part allow to change the color of the surface, the texture filters and if it is using a light that follows the camera, or a fixed directional one.
This is where the size of the texture can be defined and how the noise is generated. Note that it is possible to override the limits of the slider by Ctrl+click in the fields.
Ray marching traces a ray through a volume by taking multiple steps and sampling the volume texture at each step. It stops when the sampled value exceeds a threshold, and then performs interpolation to refine the hit point.
Presets have been create, use the slider to automatically change the setting values.
