Render speed optimisations

From Realsoft3D Wiki

Tips for faster rendering


General advice

  • Post Image Effects tab on left under Select Window [ Default Layout ]. Select an item from the library [ whichever you are using ] - eg Default Effects. Right Click then Properties - now select the SCALING tab. Set the Output Scale to 2x and 2y for fast previews or 0.5x and 0.5y for good quality renders (double image size)
  • Rendering Settings on left under Select Window [ Default Layout ]. Select an item from the library [ whichever you are using ] - eg Reasonable Quality. Right Click then Properties.
  1. Always use Stochastic AA under AA Mode (Superior to geometric)
  2. Under the Ray Tracing tab turn off all volume shadows, volumetric effects and lighting in volume if you are not using them.
  3. Recursions set to 2 or 4 dependent on how much glass being used.
  4. Undersampling of 2x2 is ok for quick render, 1x1 for good render.
  5. Thresholds for aa and undersampling can make massive differences in render times (lower numbers for better qual, 100 for fast)
  • Under Render Settings, any item being used, right click, properties, Select Post Proc Tab. Turn off/untick the Safety area tick box if not using multi processors. Select Distr Tab, turn off box rendering.
  • Under Render Settings, any item being used, right click, properties, Select Misc Tab. Mem usage to auto generally fine, caustics off, auto bright off, Geom quality low. Geom quality can make a big difference when you have a few sds objects in scene.
  • As for what settings make the biggest difference time wise when rendering - its antialiasing and threshold values. These are under the Render settings, Ray tracing Tab in the Rendering Settings section.
  • I use 3 modified render settings that may be useful: Fast ( aa at 0, no shadows ): Good ( aa at 3, shadows ) and Network ( everything cranked, network render ).
  • Shadows can be turned off too for previews - makes a big difference.
  • Raytraced shadows are preferable to mapped shadows.
  • Stick with 3 lights max in a scene if you can. Should be able to fake most situations with 3.

All the above is based on IF YOU ARE NOT specifically using the settings mentioned.


Lighting considerations

  • Try to use the minimum amount of lights needed
  • Only cast shadows from lights that really need it


Distand Lights

  • Distant lights are marginally faster to render than spot/point

Global Illumination

  • Use it only if you need it

Combined lighting rigs

  • Lighting rigs can be stored for reuse in the layers-folder, accessible in RS from the layers menu

Lighting and post effects

  • If you use soft shadows, try using the post shading studio to remove the noise in post

Model Objects


Point Density

A low point density can make rendering slower! A curve is split into segments before rendering. In the usual cubic case, each segment includes 4 points, from which the actual smooth shape is interpolated.

If the control polygon is very heavily bent to all directions, those 4 point base segments can become quite large in all dimensions. That makes raytrace optimizations harder (more curve pieces potentially travel across an examined volume of space). If the point density is sufficient, the 4 point NURBS segments become quite straight and 'thin' in some dimension(s).

This trick of increasing the point density works only when the original curve has very low point density. For example, cubic NURBS circles (or revolutions of a helix curve), which have only the minimal 4 points per 360 degrees are potentially slower than, say, 8 point circles. I would estimate that even higher point counts ( over 10 points/revolution) no longer help but start slowing down the rendering.

In the linear case, the lowest point count is naturally the fastest.



Are procedurals faster?

  • Usually not, but they don't pixelate like textures. Assuming you have enough memory and properly UV-mapped objects, I'd go with textures nine times out of ten

Post Effects

  • Anti-aliasing filtering. One trick that may reduce render time is to disable anti-aliasing by setting it to 0 in the post processing settings and instead changing the output scale. This will make the renderer render a larger image that is scaled down to the desired size after the render is complete. This scaling uses a filter and the resulting effect is similar to that of the anti aliasing filter of the renderer but often a lot faster. Setting the output scale to 0.5 doubles the internal rendering size and setting it to 0.25 quadruples it. You may experiment with different values to get the desired degree of filtering.

Hardware Issues

Do I need a better computer?


How much diffence does more ram make?

With simple scenes, the amount of RAM does not matter.

If the scene is 'medium complex' - thousands of objects and several light sources - the automatic memory usage option of Render Settings/Misc tab tries to use all available memory for precalculating optimization data. In this case, extra memory often speeds up rendering by 10-30%.

If the scene is so complex that the program starts using virtual memory during ray tracing, the amount of memory becomes a major factor. Use of virtual memory can make rendering 100 times slower.

How much difference does a faster processor make?

All processor power can be utilized quite well. Doubling the clock frequency or the number of processors usually increases rendering speed in the same proportion.

However, multi processor systems need more RAM memory. Most of the ray tracing data is not shared by processors.

Windows, Mac or Linux

The operating system does not matter. All versions ray trace with a similar speed in normal cases (if there is enough RAM memory for rendering).

What about a network