Corona Bitmap Shader

This article explains the settings and values for the Corona Bitmap shader in Cinema 4D.

Overview

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.

Shader Properties

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

UV Tiling

Mode – This allows selecting the tiling mode for the texture bitmap. Available modes are:

No tiling
UDIM
0-based UV
1-based UV
0-based two-digit UV
1-based two-digit UV
Custom pattern

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.

Crop/Placement

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.

Additional mapping

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.

Rotation W - This parameter rotates the bitmap in the Z 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.

Channel outputs

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.