This article explains the settings and values for the Corona Bitmap shader in Cinema 4D.
Corona can load bitmap textures using two supported shaders:
- Corona Bitmap shader
- Cinema 4D native Bitmap shader
Both of them produce almost identical results; however, there are some advantages of using the Corona Bitmap shader over the native Cinema 4D Bitmap shader:
- Corona Bitmaps render faster.
- Corona Bitmaps use less RAM thanks to the Out-of-core rendering feature.
- Corona Bitmap has a simplified UI and controls and additional options for texture mapping and tiling.
- Environment texture maps can be transformed using the Corona Bitmap shader.
Interpolation – Determines how we compute a color for a given UV coordinates from the bitmap. The bitmap is discrete - e.g. pixel has constant color, but the pixel has an area and UV coordinates tells us we want color from a given point. The color from such a point is computed from the surrounding pixels. Available interpolation modes are:
Nearest (low quality, fastest) – It just finds the pixel closest to the UV coordinate and returns the color.
Bilinear (faster) – Finds four closest pixels to the UV coordinate and mixes their color depending on how close they are to the UV coordinate.
Bicubic (smoother) – Similar to bilinear, but includes even more pixels in the color computation.
File – This slot allows selecting the texture bitmap using the standard file browser.
Color profile – This parameter allows the selection of the color profile that is applied to the texture map.
Embedded – Allows using the color profile included in the texture bitmap.
Linear – Changes the color profile to Linear mode.
sRGB – Changes the color profile to sRGB.
Manual Gamma – Allows to set the Input Gamma value.
Input Gamma – This parameter allows defining the input gamma value applied to the texture map.
Exposure – This parameter allows adjusting the exposure applied to the texture map
Mode – This allows selecting the tiling mode for the texture bitmap. Available modes are:
0-based two-digit UV
1-based two-digit UV
File pattern – When using a tiling mode different than No tiling, this parameter determines the filename structure for the texture maps used.
Max U size – This parameter determines the maximum tiling in the U coordinate.
Max V size – This parameter determines the maximum tiling in the V coordinate.
Ignore missing tiles – When enabled, this checkbox ignores missing texture maps if they're not found.
Mode – This parameter allows selecting between crop and placement modes.
Unit space – This parameter allows selecting between the UV (0 to 1 coordinates) and Pixels (width and height) unit space.
U – This parameter allows cropping or placing the bitmap by the U coordinates.
V – This parameter allows cropping or placing the bitmap by the V coordinates.
The U and V coordinates will turn into X and Y values when the unit space is set to Pixels.
Width – This parameter allows cropping or placing the bitmap by the width value.
Height – This parameter allows cropping or placing the bitmap by the height value.
Offset U – This parameter controls the horizontal offset for the texture map.
Offset V – This parameter controls the vertical offset for the texture map.
Length U – This parameter allows scaling the bitmap in the U coordinate.
Length V – This parameter allows scaling the bitmap in the Y coordinate.
Tiles U – This parameter allows adjusting the number of tiles in the U coordinate.
Tiles V – This parameter allows adjusting the number of tiles in the Y coordinate.
Override UVW – When enabled, this checkbox allows the use of a specific UVW channel
UVW channel – This parameter allows specifying a UVW channel.
Alpha – When a texture map is used together with constant color, alpha determines how they are mixed (alpha = 1 means only map is used, alpha = 0 means only color is used.) Here the user can select how is the alpha computed:
Image Alpha – Alpha is taken from the image (if present, e.g. in TGA/PNG) or set to 1 if missing.
RGB Intensity – Alpha is computed from RGB color.
RGB Average – Alpha is computed from the average RGB color.
None (Opaque) – Alpha is always 1.
Mono – When the output of a texture map is supposed to be a single channel (e.g. for material roughness), this is how it is computed.
RGB Intensity – Computed from RGB color.
RGB Average – Computed from average RGB color.
Image Alpha – Single channel is taken from the image (if present, e.g. in TGA/PNG) or set to 1 if missing.
RGB – Actual color output when texture map is used for color inputs (e.g. diffuse color in material).
RGB – Actual color stored in the bitmap.
RGB Intensity – RGB intensity values are used as the RGB output.
RGB Average – Average RGB values are used as the RGB output.
Image Alpha – Stored alpha in the image is used as the RGB output.