Shader glow

Problem: Shader glow brightness changes during an animation, or Shader glow brightness is different at different rendering resolutions

The shader glow auto exposure is adjusting the overall brightness of the scene for each frame. When a glowing object enters or exits the frame, the glow intensity of all objects changes.

The shader glow auto exposure causes a similar problem when rendering at different resolutions. For example, shader glow brightness is different in a high resolution final render than in a low-resolution test render.

Do one of the following:

See ShaderGlow in Render > Multi-lister .

• Set Auto Exposure OFF (under the environment’s ShaderGlow parameters), and adjust the environment shader’s ShaderGlow Glow Intensity and Halo Intensity by hand until shader glows have the correct brightness.
• Render the animation with Auto Exposure ON, and select a frame in which the shader glow brightness looks correct. Render that frame only, again with Auto Exposure ON. Open the out file (out.log in the sdl directory), and find the Glow intensity normalization factor and the Halo intensity normalization factor. Enter these two values in the environment shader’s ShaderGlow Glow Intensity and Halo Intensity parameters, and set Auto Exposure OFF.

  If you are also rendering at different resolutions, you must also scale these values based on the difference in resolutions (scale factor).

  

  For example, if you are doubling the rendering resolution, the scale factor would be 2.

  Alternatively, figure out the factor by which the *number* of pixels in the image increases, and multiply the glow by it.

  that is: (1920 x 1280) / (720 x 486) = 7.023

  Multiply your glow intensity by 7.023

Glow is missing from volume lights

Light from a volume light exists only within its volume. If the camera is not within this volume, then glow is not rendered.

Do one of the following:

• Make sure that the camera is within the volume light boundary. Use Display > Tgl camera if necessary.
• Create a glow-only point light at the same location as the volume light.

Light shining through objects

Problem: Linear and area lights shine through objects, or Light glow shines through objects.

Linear and area lights do not attempt to detect if there are shadowing objects between the light and the eye. All other light types compute this occlusion factor.

See Hide Source in Render > Multi-lister .

• Create a shader glow object with the same shape as the light, and set Hide Source ON.

  See Opacity in Render > Multi-lister .

• Set Opacity to 0 for the light.

The radius of the light may be so large that it is never completely occluded by the object that should be shadowing it.

See Light Radius in Render > Multi-lister .

• Check the Light Radius (under Common Parameters). The default setting is 1 (that is, two grid units in diameter). If Light Radius is large in relation to the geometry in the scene, reduce Light Radius to a value comparable to the size of the geometry.

Glows do not render

There is not enough memory for the renderer to calculate glows.

Do one of the following:

See Optimization.

• Reduce memory usage.

  See Hide Source in Render > Multi-lister .

• Render glows separately. Set Hide Source ON under Glow parameters, and enter the command setenv SEPARATE_GLOW_FILES 1 in the render shell. Render the scene, and composite the two image files.