This page contains information about the V-Ray PTex Texture in V-Ray for Modo.
The V-Ray PTex node can load and use 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. See also the tutorials Rendering PTex Textures from Mudbox and Rendering Vector Displacement with Object-Space PTex Textures.
UI Path: ||Shading viewport|| > Shader Tree > Add Layer button > V-Ray Textures > V-Ray PTex
Ptex File – Specifies the .ptex file to use as a texture.
Use Image Sequence – When enabled, animates the texture per frame.
Image Number – Specifies the frame number of the image to load. This channel can be animated.
Image Offset – A static offset to the image sequence.
Ifl Start Frame – Specifies the frame at which the playback of the texture will begin.
Ifl Playback Rate – A coefficient for the playback rate of the animated texture. It allows the user to slow down or speed up the playback rate of the texture.
Ifl End Condition – Specifies what happens when the final frame of an animated texture is reached.
Loop– Once the final frame is reached, the animation will jump back to the start frame.
Ping–pong – Once the final frame is reached, the animation will be played backwards towards the start and continue looping in a ping-pong manner
Hold – Once the final frame is reached, the animation will stop and stay on the final frame.
Filter Type – Specifies the type of filtering applied to the texture.
Width – Specifies the width of the filter.
Blur – Specifies the amount of the blurring.
Sharpness – Controls the amount of sharpening applied by the filter. This option is only available when the Filter Type is set to Bicubic.
Interpolation between mipmap levels – A .ptex texture may have several mipmap levels which are basically versions of the texture at different resolutions. This allows a higher resolution texture to be applied to parts of the object closer to the camera and a lower resolution version to be applied to parts of the object that are far away. When this option is enabled, V-Ray will interpolate between different mipmap levels to create a smooth seamless texture in the end.
Anisotropic filtering – Enables or disables anisotropic filtering.
Reverse vertex order – A .ptex file is generated for a specific mesh. Sometimes the program generating the PTex numbers the vertices of the mesh in the reverse order. When this happens the object is not properly textured. Enabling this option fixes the issue.
Cache Size (MB) – 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.
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 this option is disabled, the user manually specifies which channel contains which information.
Auto select alpha channel – When enabled, V-Ray automatically selects the alpha channel from the .ptex file .
Alpha Type – Specifies the mode in which alpha is applied.
Solid – All alpha information is ignored.
Alpha from texture – The information for the alpha is taken from the specified Alpha channel in the texture.
Alpha from luminance – The alpha information is taken from the Luminance of the RGB channels.
Color Space – Specifies the color space of the image.
Linear – Specifies that the color data in the file is in linear physical space, and no additional correction is necessary for rendering.
Gamma – Specifies that the color data is gamma-encoded in the file; an inverse gamma correction is applied to the color data to convert it to linear physical space for rendering, based on the gamma value.
sRGB – Specifies that the color data in the file is encoded in the sRGB color space; the standard inverse sRGB correction is applied to the colors to convert them to linear physical space for rendering. Note that sRGB color space is similar to the gamma 2.2 color space, but there are slight differences for dark colors.
Gamma – Manually specifies the gamma of the loaded texture when the gamma type is Specify and the color space is Gamma.
Color Gain – Allows you to color correct the texture by multiplying its RGB values with the RGB values specified here.
Color Offset – Allows you to color correct the texture by adding the RGB values specified here to the ones of the texture.
- More information about PTex is available here: http://www.disneyanimation.com/library/ptex/
- 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-Rays 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.
- When using PTex textures for displacement, it might be necessary to adjust the Min/M ax parameters of the Displacement Control, especially if the texture has negative colors. Otherwise the texture values might be clipped away.