View Full Version : A need for speed
February 2nd, 2010, 07:51
Can everyone post their tips for speeding up a rendering. Typically I am thinking of interior renderings. I have a great machine. I still need to be as fast as possible for render times.
I have experimented with architectural environmental shaders in the mental ray photon and light shaders of sky portals. These make the image very yellowish.
If anyone has a tip to make them less yelow would like to hear it ;)
Currently I am using black body shader on the sky portal this seems to be working very well.
Does anyone have tips to speed up renderings in general and still maintain good quality images?
March 16th, 2010, 16:08
You can adjust the yellow of the render with the Whitepoint setting in the mr Photographic Exposure control. For incandescent lighting use something between 2800 and 3300 Kelvin to make the yellowish light appear white. The default Whitepoint of 6500K is an outdoor daylight setting. Alternately you can set the color temperature of the lights to the D65 reference color and leave the mr Photographic exposure control at the default. For the Blackbody shader just set the color temp to 6500.
Combining FG and GI is usually the best and fastest indirect illumination solution. You can use a lower FG setting with GI than when using FG alone, in my experience, and since FG Diffuse Bounces are not calculated when using GI the FG pass is very fast. GI can cause its own problems with light leakage, though, but every scene is different.
For render setting, the Image Precision sliders in the Rendered Frame Window do not also adjust the Spatial Contrast setting. You may get better images and faster render times by using Samples Per Pixel of Min/Max 1 and 16 and reducing the RGB value of Spatial Contrast to .02, perhaps. This will force additional sample subdivision and the use of the Max setting more often. Some scenes may need 1 and 64, some 1/4 and 4, but experimentation on your particular scene is important.
For lights, setting the Far Attenuation value to the maximum effective distance for that light can greatly increase rendering speed. For instance if the light's intensity at 15 meters is minimal, then set the Far Attenuation to Start of 15m and End of 20m. For many scenes this is the the most significant improvement is speed you can make. Rendering your scene with just that one light (w/o Attenuation) can give you an idea if its area of influence with your current exposure settings.
April 5th, 2010, 21:56
Materials can also be a great source of rendertime woes. Ambient Occlusion forces multiple rays to be shot for every visible sample of a surface to determine the occlusion level, and this can take a long time. Use AO where it makes an impact, and only when you have the render-time to spare.
Another material issue is reflection levels; simply changing a ProMaterials Wall Paint (or new Autodesk Wall Paint) from Flat to Satin turns it into a reflective surface and can greatly increase render time. In ProMaterials and Arch & Design change the reflections level to 1 if you need simple reflectivity and fast rendering; most of the time you don't need or want more than 1. For Autodesk materials you do not have a setting per-material, however you can try reducing the overall reflection level in the Render Frame Window.
Glossy and reflective materials can be sped-up greatly by using the the "Highlights+FG only" option with the Arch & Design material, or the "Fast (interpolate)" option.
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