Corona Bitmap

When using Corona Renderer, bitmaps can be loaded using two supported nodes in the material editor:

1. Corona Bitmap
2. 3ds Max native Bitmap node

Both of them will produce almost identical results, however there are some advantages of using the Corona Bitmap over 3ds Max Bitmap node.

Corona Bitmap

Use Real-World Scale – When turned on, applies the map to objects using the real-world Width and Height values instead of UV values.

Map Channel – Allows to specify a map channel.

Offset (U) – Controls a horizontal offset.

Tiling (V) – Controls a vertical offset.

Tiling Mode:

No Tiling – For UV coordinates outside of [0,1] range the bitmap returns black color.
Repeat Tiling – The bitmap is periodically repeated outside of [0,1] range (i.e. for UV coordinates u = 0, v = 1.2 it will have the same value as u = 0, v = 0.2).
Mirrored Tiling – The bitmap is periodically repeated, but each odd repetition is mirrored (i.e. for UV coordinates u = 0, v = 1.2 it will have the same value as u = 0, v = 0.8). This means the repetition is seamless.
Clamp – For UV coordinates outside of [0,1] range the bitmap has the value of the closest valid pixel in the range (i.e. for UV coordinates u = 0, v = 5 it will have value of u = 0, v = 1). Often called "clamping".

W Rotation [deg] – Rotates the map in Z axis.

Environment mapping

Mode:

Spherical – Most common format of environment bitmaps, bitmap pixel coordinates correspond to spherical coordinates.
Screen – Tries to map bitmap in such a way that it is mapped parallel to the camera sensor.
Dome – Similar to spherical, but the sphere is not infinite, it has a given center and size.
Cross – Common format from computer games - bitmap stores environment as unfolded cube.
Mirror Ball – Mapping computed from rays reflecting from perfect mirror sphere (quite uncommon, but it was requested by the users).

Rotation [deg] – Rotates the map in X axis.

Transform from object – If used, the bitmap rotation in the environment slot (and dome origin, if dome mapping is used) is controlled by transform from a selected scene object. The other bitmap rotations are still applied on top of this.

Dome Mode

Origin X/Y/Z – Sets the centerpoint of the virtual dome in the scene, using the units specified in 3ds Max.

Radius – Sets the size of the virtual dome, using the units specified in 3ds Max. The value should be at least a bit larger than the scene size, or unexpected results may occur. A good practice is to use a value similar to the scale of the environment in the image.

Camera height – Controls how much of the image is on the "floor" of the virtual dome, and how much is on the dome itself. If you know the height of the camera when the image was taken, use that value. If you do not know the height of the camera, adjust this by eye to minimize distortion on the floor of the dome.

Crop/Place

On – Makes crop/place active.

Crop – Makes Crop active.

Place – Makes Place active.

View Image – Opens a window that shows the bitmap surrounded by a region outline with handles at its sides and corners

U/V – Crops/Places the bitmap by UV coordinates.

Width/Height – Crops/Places the bitmap by width/height values.

Channel Outputs

Alpha – When map is used together with constant color, alpha determines how they are mixed (alpha = 1 - only map is used, alpha = 0 only color is used.). Here the user can select how is the alpha computed:

None (Opaque) – Alpha is always 1.
RGB Intensity – Alpha is computed from RGB color.
Image Alpha – Alpha is taken from image (if present, e.g. in TGA/PNG) or set to 1 if missing.

Mono – When the output of map is supposed to be a single channel (e.g. for material roughness), this is how we compute it.

RGB Intensity – Computed from RGB color.
Image Alpha – Single channel is taken from image (if present, e.g. in TGA/PNG) or set to 1 if missing.

RGB – Actual color output when map is used for color inputs (e.g. diffuse color in material).

RGB – Actual color stored in bitmap.
ImageAlphaasgray – Gray color is computed from alpha stored in the image.

Bitmap

Load Map – Selects the bitmap using the standard file browser.

Reload – Reloads the bitmap file using the same name and path. You don’t need to use the file browser to reload the bitmap after you've updated it in your paint program. Clicking reload for any instance of the map updates the map in all sample slots and in the scene.

Filtering

Blur – Controls the blurriness of the image.

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 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 surrounding pixels.

Bilinear (faster) – Finds four closest pixels to the UV coordinate and mix 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.
Nearest Neighbour (low quality, faster) – It just finds pixel closest to the UV coordinate and returns the color.

Corona Bitmap - Blurring