This page provides information on the V-Ray Bitmap Texture.
Overview
The VRayBitmap map can be used to load high dynamic range images (HDRI) and map them onto the environment. V-Ray supports most of the standard HDRI-environment mapping methods. This texture can also be used to load other file formats.
UI Path: Texture > V-Ray > VRayBitmap
Tiled OpenEXR and TIFF Files
This texture can also be used to efficiently load tiled OpenEXR and tiled TIFF files (tiled TIFF files usually have a .tx or .tex extension). Tiled OpenEXR and TIFF files allow only portions of the textures to be loaded at various resolutions. This allows V-Ray to load only the parts of the textures that are needed for the rendering.
You can convert many common image file formats to tiled OpenEXR files using the img2tiledexr tool. You can also convert all files in a scene using the V-Ray Bitmap to VRayBitmap converter script. Conversion to tiled TIFF can be done using the maketx tool from the OpenImageIO library.
Tiled TIFF files have the advantage that they can store 8-bit color components, whereas OpenEXR stores at least 16 bits. This means that tiled 8-bit TIFF textures are smaller on the disk and take up less RAM while rendering.
Tags and Environment Variables in Bitmap Names
VRayBitmap allows the use of named tags enclosed with the characters < and >, which are replaced at render time with other strings.
Tags for Multi-Tiles
Some modeling applications allow to specify a different bitmap file for different portions of a model based on the UV coordinates of that model. For example, one file may be used for UVs in the range [0,0] x (1,1), another file may be used for UVs in [1,0] x (2,1) and so on. There are several ways to specify the correct file for each tile, and in each case, a different format for the file name is used in the File node. This is done by using special tags in the file name, which are replaced at render time with a particular string based on the UVs of the current shading point.
In the following section, we assume that each UV tile has unique integer coordinates (u,v) based on the integer part of the UVs inside it. For example, the UV tile [0,0] x (1,1) has coordinates (0,0), the UV tile [1,0] x (2,1) has coordinates (1,0) and so on.
Upper-case tags usually assume the tile coordinates start from 1, whereas lower-case tags assume the tiles start from 0.
Mari Tiles and the <UDIM> Tag
Mari forms the file name of textures using a four-digit number equal to 1000+(u+1+v*10). So the UV tile [0,0] x (1,1) is assigned the number 1001, UV tile [0,1] x (1,2) is assigned 1011 and so on. To specify a Mari-style tiled texture, use the <UDIM> tag in the file name, which is then replaced with the respective four digits, for example, my_texture_<UDIM>.exr becomes my_texture_1001.exr and so on during rendering.
Mudbox Tiles and the <UVTILE> Tag
Mudbox can form the file name in many ways, but the default format is to use _uU_vV in the file name where U=u+1 and V=v+1 are the tile coordinates plus one. So the UV tile [0,0] x (1,1) is marked with _u1_v1, UV tile [0,1] x (1,2) is marked with _u1_v2 and so on. To specify this format, use the <UVTILE> tag in the file name. If you use lower case letters <uvtile> , then the tile coordinates will start from 0, instead of one, so tile [0,0] x (1,1) will be resolved to _u0_v0 and so on. For example, my_texture<UVTILE>.exr becomes my_texture_u1_v1.exr and so on during rendering.
The $U and $V Tags
You can also specify the u and v coordinates of the tiles separately by using the $U and $V tags. Each of them is expanded to the respective 1-based coordinate of the tile. For example, if the file name is specified as my_texture_$U_$V.exr, this becomes my_texture_1_1.exr and so on. You can use lower-case tags to make the tile coordinates start from zero, instead of 1, for example my_texture_$u_$v.exr becomes my_texture_0_0.exr and so on.
You can put a number right after the $ sign to specify how many digits you want in the resulting tile coordinates, for example my_texture_$2U_$2V.exr is expanded to my_texture_01_01.exr and so on.
The <frameNum> tag
The frameNum tag can be used to specify an image sequence. V-Ray loads a sequence from the same path. To use the frameNum tag, just add <frameNum> to your texture filename.
For example, if the first image in the sequence is located at C:\textures\myImage.0001.png, change the string to C:\textures\myImage.<frameNum>.png and V-Ray will look for an image that corresponds to each frame within the animation range.
Environment Variables
You can include environment variables in the form ${VAR_NAME} which are replaced with the value of the respective environment variable during rendering. For example, if the file name is specified as ${TEX_PATH}\${PROJ_FOLDER}\mytexture.exr, then V-Ray will look up the environment variables TEX_PATH and PROJ_FOLDER and replace the tags with their values. Suppose that TEX_PATH is set to c:\textures and PROJ_FOLDER is set to proj1, then the final bitmap file name will be expanded as c:\textures\proj1\mytexture.exr
Bitmap Properties
Bitmap – Specifies the file name from which the bitmap is loaded. Currently supported formats are HDR, EXR, PNG, BMP, TGA, SGI, JPG, PIC, TIF, PSD, VRIMG. Image file lists in the form of IFL files are also supported.
Filter – Specifies the V-Ray internal texture filtering method. See the Filtering examples below. Possible values are:
No Filter
Mip-map – Pyramidal MIP map filtering is used to compute the texture color. Can be blurry for textures seen at grazing angles.
Area
Elliptical – High quality anisotropic MIP map texture filtering that reduces blurring and aliasing artifacts. Can be slower compared to the Isotropic filtering.
Sharp Mip-map – Sharper and more accurate version of the Mip-map filtering. Produces results that are closer to the results with disabled filtering but with less AA samples required.
Interpolation – Determines how the image is interpolated from the pixel values. See the Examples for a demonstration of this effect. Possible values are:
Bilinear – Image values are interpolated from four pixels in the bitmap. This is the fastest interpolation method, but the result is not continuous (non-smooth) and may produce artifacts when the map is used for displacement or bump mapping.
Bicubic – Image values are interpolated from sixteen pixels in the bitmap. This is the slowest method, but the results are smooth without too much blur.
Biquadratic – Image values are interpolated from nine pixels in the bitmap. This method is faster than the Bicubic interpolation, but may smooth the image too much.
Filter Blur – Additional multiplier which controls filter blurring, especially useful with the mapping source feature. The higher the value, the more blurred the texture renders and the less render time it takes, and vice versa. A value of 0.01 means no filtering, but leads to increased render times. If a Bitmap is connected to the VRayBitmap as a mapping source, the Filter multiplier option serves as a multiplier for the Blur parameter of the Bitmap. For example, if the Bitmap Blur parameter is set to 10, and the VRayBitmap Filter multiplier is set to 0.1, the texture blur amount is effectively, 1.
Color Space – Specifies the color space for the loaded image file. The value is automatically selected when loading a new file by looking for the strings "_lin_srgb", "_srgb" and "_raw" in the file name. It also considers the file extension. You can manually modify the value.
High dynamic range images (hdr, exr) will load with Gamma corrected type, unless "_srgb" is found in the name string - then sRGB Type will be automatically set instead. All other file types (8-bit images like jpg, png, and other files) will automatically load with types according to the string found in their file names: sRGB for "_srgb", Linear for "_lin_srgb". Additionally, all files with any extension that have "_raw" string in their name load with Type Linear. This way the most appropriate type respective to the loaded file is applied.
sRGB
Linear
Gamma corrected
Gamma – A gamma–correction value for the image. For example, if the bitmap was saved to disk with a 2.2 gamma correction, you need to enter 0.4545 to remove that correction for the rendering.
Allow Negative Colors – If disabled, negative colors are clamped. Enable to allow negative colors.
Output
Color Mult – Corrects the color of the texture by multiplying the RGB color values in the texture with the RGB color values specified here. A texture map can be assigned here.
Color Offset – Corrects the color of the texture by adding the RGB color values specified here to the RGB color values of the texture. A texture map can be assigned here.
Invert – Makes the output map hues inverted.
Alpha Source – Determines how the texture alpha is computed:
Bitmap – From the alpha channel of the bitmap image, if present (and 1.0 if the image has no alpha channel);
Intensity – The alpha is taken from the intensity of the bitmap image colors (red+green+blue)/3;
Opaque – The alpha channel of the bitmap image is ignored and the VRayBitmap texture always returns 1.0 for alpha.
Alpha Mult –
Alpha Offset –
No UVs Color – Specifies a default color used for polygons with no valid UVs. In case the map is not tiled, specifies a default color that is used outside the texture square. When a texture is selected, it overrides the color.
Time
These options allow you to control animated textures.
Start Frame – Specifies the beginning of the texture animation. The frame number specified here will be played at the first frame of the scene animation.
Playback Rate – Controls the animation speed of the texture as fraction of the actual animation speed. A value of 1 means that the texture animation will run at regular speed. A value of 2 means that the texture animation will run twice as fast as the scene animation.
End Condition – Allows you to control what happens when the last frame of the animated texture is reached. The available options are:
Loop – The animation will start again from the frame specified in the Start Frame option
Ping-pong – The animation will be played backwards until it reaches the the frame specified in the Start Frame option and then play forward again
Hold – The animation will stop at the last frame and it will be displayed until the end of the scene animation.
Mapping
Tile – Specifies how the texture is repeated:
No tiling – No repetition is done;
Tile in UV – Repeats the texture in both U and V axis;
Tile in U – Repeats the texture only on the U axis;
Tile in V – Repeats the texture only on the V axis;
Tile in UV - No Filter –
Placement Type – Specifies how the mapping controls below work:
Full – Uses the whole bitmap.
Crop – Uses a section of the bitmap.
Place – Adjusts of the position of the image.
Tile U/V – Adjust the tiling along the U and V axis.
U/V – Adjusts the texture location - specifies the location of the top left corner of the image.
Width/Height – Adjusts the width and height of the texture or crop area.
Jitter – Introduces random offset.
UV Noise
UV Noise On – Enables noise in the pattern of the texture.
Animate UV Noise – Enables animation of the noise effect.
UV Noise Amount – Specifies the strength of the noise. A value of 0 means no noise, while higher values introduce increasing noise.
UV Noise Levels – Specifies how many times the noise is applied to the texture.
UV Noise Size – Allows you to scale the noise according to the object the texture is applied to.
UV Noise Phase – Allows you to control the animation speed of the noise effect, if the noise is animated.
