This page provides information on the Color Mapping rollout of the V-Ray Main render settings.
Color mapping (sometimes also called tone mapping) can be used to apply color transformations on the final image colors. Sometimes an image can contain a higher range of colors that can be displayed on a computer screen. Color mapping has the task of re-mapping the image values to be suitable for display purposes.
UI Path: ||V-Ray Main render settings|| > Color Mapping rollout
Type – The type of transformation used. These are the possible types:
Linear Multiply – Simply multiplies the final image colors based on their brightness without applying any changes.
Exponential – Saturates the colors based on their brightness. This can be useful to prevent burn-outs in very bright areas (for example, around light sources, etc.). This mode will clamp colors so that no value exceeds (255, or 1 in floating point value).
HSV exponential – Very similar to the Exponential mode, but it will also preserve the color hue and saturation, instead of washing out the color towards white.
Intensity exponential – Similar to the Exponential mode, but it will preserve the ratio of the RGB color components and will only affect the intensity of the colors.
Gamma correction – Applies a gamma curve to the colors. In this case, the Multiplier influences the colors before they are gamma-corrected. The Inverse gamma is the inverse of the gamma value (i.e. for gamma 2.2, the Inverse gamma must be 0.4545). This is a deprecated mode, do not use it. For more information, see Example: Linear Work Flow.
Intensity gamma – Applies a gamma curve to the intensity of the colors, instead of each channel (RGB) independently. This is a deprecated mode, do not use it.
Reinhard – A blend between exponential-style color mapping and linear mapping. If the Burn value is 1.0, the result is linear color mapping and if the Burn value is 0.0, the result is exponential-style mapping.
The default settings for color mapping are such that V-Ray renders out the image in linear space (Reinhard color mapping with Burn value 1.0 produces a linear result).
Multiplier – Allows you to control the overall brightness by multiplying each RGB value with the value here
Burn Value – Controls the Reinhard Mapping. Value of 1 results in a Linear color mapping a value of 0 results in Exponential color mapping. Values between 1 and 0 blend the two color mapping modes.
Gamma – Allows you to control the gamma correction for the output image regardless of the color mapping mode. Note: The value here is the inverse of the one used for the Gamma correction color mapping type. For example, to correct the image for a 2.2-gamma display, you should set the Gamma parameter simply to 2.2.
Affect background – When disabled, color mapping will not affect colors belonging to the background.
Mode – The possible values for this option are:
Color mapping and gamma – Both color mapping and gamma are burned into the final image.
None – Neither color mapping nor gamma are burned into the final image. However, V-Ray will proceed with all its calculations as though color mapping and gamma are applied (e.g. the noise levels will be corrected accordingly). This can be useful, for example, if you know that you will apply some color correction to the image later on, but wish to keep the rendering itself in linear space for compositing purposes.
Color mapping only (no gamma) – Only color mapping is burned into the final image, but not the gamma correction. This is the default option. V-Ray will still proceed to sample the image as though both color mapping and gamma are applied, but will only apply the color correction (Linear, Reinhard, etc.) to the final result.
Note: The Clamp output option will have an effect regardless of the value of the Mode option.
Clamp output – When enabled, colors will be clamped after color mapping. In some situations, this may be undesirable: for example, if you wish to anti-alias HDR parts of the image as well, turn clamping.
Clamp level – Specifies the level at which color components will be clamped if the Clamp output option is on.
This example demonstrates the differences between the color mapping modes.
As visible in the above images, the Linear mapping method clamps bright colors to white, causing bright parts of the image to appear "burnt out". Both the Exponential and HSV exponential modes avoid this problem. While the Exponential mode tends to wash out the colors and desaturate them, the HSV exponential mode preserves the color hue and saturation.
Note: the Sibenik Cathedral model was created by Marko Dabrovic ( http://www.rna.hr ) and was one of the models for the CGTechniques Radiosity competition.
This example shows the same image rendered with 3 different settings for Gamma and Liner Workflow.