This page provides information on the V-Ray PTex Texture.
The V-Ray Ptex loads and uses PTex textures with V-Ray. PTex is a mapping system that applies a separate texture to each face of a subdivision or polygon mesh and therefore requires no UV assignment. A PTex file can store an arbitrary number of textures along with mipmaps and adjacency data used for filtering across face boundaries. For more information on the PTex concept, see the Notes section below.
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The TexPtex node provides inputs for controlling various texture properties. They correspond to parameters in the section below.
Ptex File – Specifies the .ptex file to use as a texture.
Color Space – Specifies the color space used.
Gamma Corrected – The bitmap data is gamma corrected with the specified gamma value specified by the Texture input gamma attribute, so V-Ray needs to remove this gamma correction for rendering.
Linear – The bitmap data is already in physical linear space, so no correction required and none is performed.
sRGB – The bitmap data is in the sRGB color space, so V-Ray needs to convert it to linear physical space for rendering.
Gamma – Specifies the gamma value used to control the luminance of the image when the color space is set to Gamma Corrected.
Gain – Color corrects the texture by multiplying the RGB color values specified here to the RGB color values in the texture.
Offset – Color corrects the texture by adding the RGB color values specified here to the RGB color values in the texture.
Auto Select Color Channels – A PTex may have an arbitrary number of channels and there is no sure way to determine which channel contains which information. When this option is enabled, V-Ray tries to select the correct channel for Red, Blue and Green. When disabled, the user manually specifies which channel contains which information.
R Channel – The index of the channel that is used as a red channel.
G Channel – The index of the channel that is used as a green channel.
B Channel – The index of the channel that is used as a blue channel.
Auto Select Alpha Channels – When enabled, V-Ray automatically selects the alpha channel from the PTex file.
A Channel – The index of the channel that is used as an Alpha channel.
Alpha Type – Specifies where to take alpha from.
Image Number – Specifies the frame number of the image to load. This attribute can be animated.
Image Offset – Specifies a static offset to the image sequence.
Use Image Sequence – When enabled, animates the texture per frame.
Ifl Start Frame – Specifies the starting frame for the sequence.
Ifl Playback Rate – Specifies the playback rate.
At Sequence End – Specifies what happens when the sequence end is reached.
Loop – The texture is looped to start from the beginning.
Ping Pong – The texture is looped alternatively forward and backward.
Hold – The last image in the sequence is used for all subsequent frames.
Filter Type – Specifies the type of filtering to apply to the texture.
Anisotropic Filtering – Enables anisotropic filtering.
Interpolation Between Mipmap Levels – Enables the interpolation between mipmap levels.
Width – Specifies the width of the filtering.
Blur – Specifies the blur of the filtering.
Cache Size (mbs) – The information in a PTex file is compressed for storage. In order to be used it has to be uncompressed and stored in the RAM. This parameter controls how much memory (in MB) is available for the current texture. If the value is large enough for the whole texture the information is extracted only once and is stored during the entire rendering. Otherwise the information is constantly read from the hard drive, extracted and used when necessary. Low value for this parameter may cause large PTex files to render slowly.
More information about PTex is available here.
- PTex files are strongly connected to the topology of an objects's mesh. Therefore any modification which change the topology will break the rendering of the PTex texture. If you want to smooth the object, you can use V-Ray's own subdivision/displacement.
- When using PTex textures for displacement, small cracks might appear along polygon edges because of slightly different filtering applied to the PTex texture on adjacent polygons. Setting the filter width to 0.0 will improve the situation, but will cause the most detailed mip-map level of the PTex file to be loaded thus increasing the required memory.