Category: Rendering


Constant vs. Sprite

For a lot of unshaded renders, where lighting is not important, the Sprite material is a better choice than Constant, for the simple reason that transparencies in Sprite don’t count toward your ray-traced refraction count, but transparencies in Constant do. If you’ve got a lot of transparent layers (using a particle system, say) with cutout masks, Sprite material is the way to go.

Displacement Settings in Softimage

OK, here’s an annoying tidbit you’ll want to know about if you’re rendering with displacements in mental ray:  when using the “Fine” displacement method, you’ll get more satisfactory results with fewer polygons if you set “Sharpness” to 100%.

via this article on CGSociety.org, I’ve learned about a new method for calculating bounce light that’s  much faster than current solutions like ambient occlusion, final gather or global illumination. Point-based lighting, if I understand the article correctly, involves a pre-pass to create and cache a point cloud based on the scene geometry which can then be used at render time to calculate bounce light, color bleed, ambient occlusion, and IBL 4x to 10x faster than conventional rendering solutions.

Very interesting! It sounds like there’s a tradeoff in that the point cloud requires a lot of disk space (300Gb for some Toy Story 3 shots!) and is slightly less accurate than geometry-based methods (note overall darkening, as well as the shadow detail in the lion’s crotch in the example above). The article describes the technique as being most useful in very complex scenes where ray tracing/ radiosity methods are impossible. I will be very interested to see if this technology makes its way into other rendering packages (sounds like it is already available in the RMan commercial release).

2D or 3D?

Today I began redoing the main title animation with new typesetting from the designer, and as I was setting out on the somewhat time-consuming process of rebuilding the meshes from the EPS, I asked myself, should I instead try to do this title entirely in Nuke? The rendering time is pretty steep, the modeling of the letterform meshes takes much too long, and the design itself is very subtle and barely needs 3D to function. Working entirely in Nuke would be way faster, and finding faster solutions is something I’m trying to make a habit of. View Full Article »

Jack Daniel’s “Label Story”

A lovely bit of NPR/mixed media rendering in the style of an etching.

Jack Daniel’s “Label Story”: “Old No. 7″ from Brand New School on Vimeo.

Light Blocking

This is a great tip for setting up lights quickly, via Andrew at 3dLight: create a new render pass and override all materials to 18% grey, either lambert or with a slight phong when highlight placement is critical. Losing your heavy materials will speed iterations, and the uniform medium grey makes it easier to judge light values on their own.

Light Blocking tip from 3DLight

After reading up on the difference between regular, sorted, and segmented ray-traced shadows in mental ray, I have learned that they are increasingly complex and more accurate methods of calling shadow shaders to compute the shadow result. The segmented method also calls volume shaders while the others don’t, so you’ll need it to create volumetric shadow effects with rt shadows. Expensive! Regular and sorted shadows–as I understand–disregard the volume, both any volume shaders, and, it appears, the relative positions of the shadow casting objects.

In my case, I didn’t have volumetric effects but rather several shadow-casting cards (gobos or cookies, we used to call them) throwing a shadow on a surface. Just one card by itself by itself renders correctly with all three methods, but a second card won’t cast accurate shadows except with segmented.

Softimage wiki: Rendering Methods for Shadows and 3DAnimation Artist: mr for Maya Notes

Moving through HDRs

Here’s a tip Paul Debevec shared with me that I want to make sure I remember. “If we’re using spherical environment maps for IBL lighting,” we asked, “but your subject is moving through the environment, how do you get the lighting to reflect that? If you have multiple IBL maps for different points inthe environment, all well and good, but how do you transition from one to the other?”

The answer was one of those solutions that seems so obvious in retrospect. Using photogrammetry or set measurements or what ever you have, build standin geometry that roughly matches the environment. Then you reproject textures from the IBL spheres onto this geometry, based on their world position. (I’m not sure what off-the-shelf tool one would use for this, but I aim to find out.)  At this point, you can use the textured geometry as the IBL source, or you can take it a step further and project the IBL back onto an environment sphere centered on the moving subject. I don’t fully understand the resason for this step although I can see how it would speed subsequent rendering significantly. Leaving placeholder geometry as the lightsource would be more expensive but it could get better results for subjects that interact with their environment: more correct reflections, for example.

Looks to attempt

For the fruitbowl still life lighting challenge

  • Color photograph, realistic materials
  • Silver gelatin print
  • Sin City contrasty b/w
  • Lichtenstein big color halftone dots (in screen space and in object space)
  • Marker grafitti
  • Different Metals
  • Engraved illustration
  • ballpoint pen sketch

GO!

Birn’s lighting challenges

Folllowing up on my variations idea, I should probably just hit these challenges first. Free, ready to go… what if I spent 30 minutes a night pushing one of these forward until it looked great? Maybe giving myself a short, delimited window of time would give me the psychological breathing space/impetus to attempt and finish the project.

And if I noted what work I had completed in that 30 minute chunk, after a year I’d have a pretty good idea of how long these tasks take.

The full list of lighting challenges on 3D Render.

Powered by WordPress. Theme: Motion by 85ideas.