Method

CoglPipelineset_layer_combine

Declaration [src] 

gboolean
cogl_pipeline_set_layer_combine (
  CoglPipeline* pipeline,
  int layer_index,
  const char* blend_string,
  GError** error
)

Description [src]

These are all the functions available for texture combining:

  • REPLACE(arg0) = arg0
  • MODULATE(arg0, arg1) = arg0 x arg1
  • ADD(arg0, arg1) = arg0 + arg1
  • ADD_SIGNED(arg0, arg1) = arg0 + arg1 - 0.5
  • INTERPOLATE(arg0, arg1, arg2) = arg0 x arg2 + arg1 x (1 - arg2)

  • SUBTRACT(arg0, arg1) = arg0 - arg1

 DOT3_RGB(arg0, arg1) = 4 x ((arg0[R] - 0.5)) * (arg1[R] - 0.5) +
                             (arg0[G] - 0.5)) * (arg1[G] - 0.5) +
                             (arg0[B] - 0.5)) * (arg1[B] - 0.5))

-

 DOT3_RGBA(arg0, arg1) = 4 x ((arg0[R] - 0.5)) * (arg1[R] - 0.5) +
                              (arg0[G] - 0.5)) * (arg1[G] - 0.5) +
                              (arg0[B] - 0.5)) * (arg1[B] - 0.5))

The valid source names for texture combining are:

Layer Combine Examples:

This is effectively what the default blending is:

RGBA = MODULATE (PREVIOUS, TEXTURE)

This could be used to cross-fade between two images, using the alpha component of a constant as the interpolator. The constant color is given by calling cogl_pipeline_set_layer_combine_constant().

RGBA = INTERPOLATE (PREVIOUS, TEXTURE, CONSTANT[A])

You can’t give a multiplication factor for arguments as you can with blending.

Parameters

layer_index

Type: int

Specifies the layer you want define a combine function for.

blend_string

Type: const char*

A Cogl blend string describing the desired texture combine function.

The data is owned by the caller of the method.
The value is a NUL terminated UTF-8 string.
error

Type: GError **

The return location for a recoverable error.

The argument can be NULL.
If the return location is not NULL, then you must initialize it to a NULL GError*.
The argument will be left initialized to NULL by the method if there are no errors.
In case of error, the argument will be set to a newly allocated GError; the caller will take ownership of the data, and be responsible for freeing it.

Return value

Type: gboolean

TRUE if the blend string was successfully parsed, and the described texture combining is supported by the underlying driver and or hardware. On failure, FALSE is returned and error is set.