Distant-diffuse lighting effect

Use the distant-diffuse lighting effect to create an image that appears to be a reflective surface with where the light source appears to be coming from a long distance (like the sun or overhead lights) and the light is reflecting in all directions. This effect uses the alpha channel as a height map and lights the image with a distant light source.

The color of the output bitmap is a result of light color, light position, and the surface geometry of the image. The alpha channel output for each pixel with diffuse lighting is always 1.0.

The CLSID for this effect is CLSID_D2D1DistantDiffuse.

Example image

The example here shows the input and output images of the distant-diffuse lighting effect.

Effect example screenshot the input and output images of the distant diffuse lighting effect.

Effect properties

Display name and index enumerationType and default valueDescription

Azimuth

D2D1_DISTANTDIFFUSE_PROP_AZIMUTH

FLOAT

0.0f

The direction angle of the light source in the XY plane relative to the X-axis in the counter clock wise direction. The units are in degrees and must be between 0 and 360 degrees.

Elevation

D2D1_DISTANTDIFFUSE_PROP_ELEVATION

FLOAT

0.0f

The direction angle of the light source in the YZ plane relative to the Y-axis in the counter clock wise direction. The units are in degrees and must be between 0 and 360 degrees.

DiffuseConstant

D2D1_DISTANTDIFFUSE_PROP_DIFFUSE_CONSTANT

FLOAT

1.0f

The ratio of diffuse reflection to amount of incoming light. This property must be between 0 and 10,000 and is unitless.

SurfaceScale

D2D1_DISTANTDIFFUSE_PROP_SURFACE_SCALE

FLOAT

1.0f

The scale factor in the Z direction. The surface scale is unitless and must be between 0 and 10,000.

Color

D2D1_DISTANTDIFFUSE_PROP_COLOR

D2D1_VECTOR_3F

{1.0f, 1.0f, 1.0f}

The color of the incoming light. This property is exposed as a D2D1_VECTOR_3F – (R, G, B) and used to compute LR, LG, LB.

KernelUnitLength

D2D1_DISTANTDIFFUSE_PROP_KERNEL_UNIT_LENGTH

D2D1_VECTOR_2F

{1.0f, 1.0f}

The size of an element in the Sobel kernel used to generate the surface normal in the X and Y direction. This property maps to the dx and dy values in the Sobel gradient. This property is a D2D1_VECTOR_2F (Kernel Unit Length X, Kernel Unit Length Y) and is defined in (device-independent pixels (DIPs)/Kernel Unit). The effect uses bilinear interpolation to scale the bitmap to match size of kernel elements.

ScaleMode

D2D1_DISTANTDIFFUSE_PROP_SCALE_MODE

D2D1_DISTANTDIFFUSE_SCALE_MODE

D2D1_DISTANTDIFFUSE_SCALE_MODE_LINEAR

The interpolation mode the effect uses to scale the image to the corresponding kernel unit length. There are six scale modes that range in quality and speed.

 

Scale modes

EnumerationDescription
D2D1_DISTANTDIFFUSE_SCALE_MODE_NEAREST_NEIGHBORSamples the nearest single point and uses that. This mode uses less processing time, but outputs the lowest quality image.
D2D1_DISTANTDIFFUSE_SCALE_MODE_LINEARUses a four point sample and linear interpolation. This mode outputs a higher quality image than nearest neighbor.
D2D1_DISTANTDIFFUSE_SCALE_MODE_CUBICUses a 16 sample cubic kernel for interpolation. This mode uses the most processing time, but outputs a higher quality image.
D2D1_DISTANTDIFFUSE_SCALE_MODE_MULTI_SAMPLE_LINEARUses 4 linear samples within a single pixel for good edge anti-aliasing. This mode is good for scaling down by small amounts on images with few pixels.
D2D1_DISTANTDIFFUSE_SCALE_MODE_ANISOTROPICUses anisotropic filtering to sample a pattern according to the transformed shape of the bitmap.
D2D1_DISTANTDIFFUSE_SCALE_MODE_HIGH_QUALITY_CUBICUses a variable size high quality cubic kernel to perform a pre-downscale the image if downscaling is involved in the transform matrix. Then uses the cubic interpolation mode for the final output.

 

Note  If you don't select a mode, the effect defaults to D2D1_DISTANTDIFFUSE_SCALE_MODE_LINEAR.

Sample code

For an example of this effect, download the Direct2D lighting effects sample.

Requirements

Minimum supported clientWindows 8 and Platform Update for Windows 7 [desktop apps | Windows Store apps]
Minimum supported serverWindows 8 and Platform Update for Windows 7 [desktop apps | Windows Store apps]
Headerd2d1effects.h
Libraryd2d1.lib, dxguid.lib

 

Related topics

ID2D1Effect

 

 

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