Plasma is a small reference application used to exercise Aurora, without requiring the use of a full Autodesk application or USD Hydra scene delegate. Plasma can load OBJ files like the one shown below, along with certain material properties. See the usage instructions below. The McGuire Computer Graphics Archive is a good resource for OBJ files.
Plasma has the same system requirements as Aurora. In particular, a GPU with support for DirectX Raytracing or Vulkan Ray Tracing is required.
At this time, interactive use of Plasma is only supported on Windows. For Linux, command-line single image rendering is available as described below, and interactive support is coming soon.
| Feature | Input |
|---|---|
| Load an OBJ File | CTRL-O key OR Drag and drop OR File path as first command line argument |
| Load an environment image (HDR format) | CTRL-E key OR Drag and drop |
| Load a MaterialX document (.mltx) | CTRL-M key: Applies to all loaded objects M: Reload the previous document R key: Reset materials to original |
| Save screenshot as PNG (to last accessed directory) | S key |
| Set to Full Screen | F11 key |
| Toggle v-sync | V key |
| Toggle animation | Space key |
| Toggle tone mapping | T key |
| Toggle directional light | L key |
| Toggle diffuse only rendering | D key |
| Toggle denoising | SHIFT-D key |
| Toggle transparent shadows * | O key |
| Toggle ground plane | G: matte shadow SHIFT-G: matte reflection |
| Cycle importance sampling | I (letter) key, cycles in the following order: 1) Multiple importance sampling (MIS) 2) BSDF importance sampling 3) Environment light importance sampling |
| Adjust exposure (½ stop increments) | + key (increase) and - key (decrease) |
| Adjust max luminance for samples (firefly clamping) | CTRL+ key (increase) and CTRL- key (decrease) (full stops starting at 1000 luminance) |
| Adjust trace depth (path length) ** | [ key (increase) and ] key (decrease) (default 5, range is [1, 10]) |
| Display debug buffers (AOVs) | ~ = Output (beauty) 1 = Output with errors 2 = ViewZ (depth) 3 = Normals 4 = Base Color 5 = Roughness 6 = Metalness The following are used for denoising: 7 = Diffuse radiance 8 = Diffuse hit distance 9 = Glossy radiance 0 = Glossy hit distance |
| Orbit View | Left click and drag |
| Pan View | Right click and drag |
| Dolly View | Middle click and drag OR Mouse wheel |
| Fit View to Scene | F key |
| Quit | ESC key |
* This is a performance optimization.
** It may be necessary to increase trace depth for overlapping transparent / transmissive surfaces, at the cost of performance.
The following command renders an output image with the specified scene file. The optional --renderer hgi argument enables the HGI backend in the renderer, with DirectX used as the default backend. On Linux, you must use the HGI backend.
Plasma --output {OUTPUT_FILE_NAME.png} --scene {INPUT_SCENE.obj} [--renderer hgi]
The following properties from OBJ MTL files are supported. OBJ MTL properties not listed here are ignored. Materials are converted to use the Autodesk Standard Surface material model.
| Standard Surface | OBJ MTL File | Notes |
|---|---|---|
| base_color | Kd / map_Kd | Image supported. |
| metalness | Pm | |
| specular_color | Ks | |
| specular_roughness | Pr / map_Pr | Image supported. "Ns" for non-physical shininess is not supported; use Pr instead. |
| specular_IOR | Ni | This is the index of refraction, e.g. 1.5 is a good value for glass. |
| transmission | Tr / d | The two values are inverses of each of other, i.e. d of 1 is the same as Tr of 0, i.e. opaque. It may be necessary to increase the trace depth (described above) for certain models to look correct. Tr / d in OBJ are typically used for opacity (transparency) but here they are used for transmission instead, which is more interesting, e.g. for refraction. If values for both are present, the value for d will be used. |
| transmission_color | Tf | Black (the default) is assumed to be useless and will be interpreted as white (no tint). |
| opacity | map_d | Image only. This is different from transmission. In Standard Surface, opacity refers to transparency, which is simple alpha blending. It was determined that it is more useful for map_d to be used for opacity, to support cutouts. |
| normal | bump / norm | Image only, and it must be a normal map (not a height map) |