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Spot-diffuse lighting effect

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Use the spot-diffuse lighting effect to create an image that appears to be a non-reflective surface with where the light source is limited to a directed cone of light and the light is scattered in all directions. This effect uses the alpha channel as a height map and lights the image with a spot light source.

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

The CLSID for this effect is CLSID_D2D1SpotDiffuse.

Example image

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

effect example screenshot that shows

The effect calculates the final output pixel values are calculated using these equations:

output bitmap calculation

Where:

kd = diffuse lighting constant. Specified by the user.
normal vector symbol. = surface normal unit vector, a function of x and y.
light vector symbol. = unit vector pointing from surface to light.
Lr, Lg, Lb = the light color in RGB components.

Effect properties

Display name and index enumeration Type and default value Description
LightPosition
D2D1_SPOTDIFFUSE_PROP_LIGHT_POSITION
 D2D1_VECTOR_3F
{0.0f, 0.0f, 0.0f}
 The light position of the point light source. The property is a D2D1_VECTOR_3F defined as (x, y, z). The units are in device-independent pixels (DIPs) and are unbounded.
PointsAt
D2D1_SPOTDIFFUSE_PROP_POINTS_AT
 D2D1_VECTOR_3F
{0.0f, 0.0f, 0.0f}
 Where the spot light is focused. The property is exposed as a D2D1_VECTOR_3F with (x, y, z). The units are in DIPs and the values are unbounded.
Focus
D2D1_SPOTDIFFUSE_PROP_FOCUS
 FLOAT
1.0f
 The focus of the spot light. This property is unitless and is defined between 0 and 200.
LimitingConeAngle
D2D1_SPOTDIFFUSE_PROP_LIMITING_CONE_ANGLE
 FLOAT
90.0f
 The cone angle that restricts the region where the light is projected. No light is projected outside the cone. The limiting cone angle is the angle between the spot light axis (the axis between the LightPosition and PointsAt properties) and the spot light cone. This property is defined in degrees and must be between 0 to 90 degrees.
DiffuseConstant
D2D1_SPOTDIFFUSE_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_SPOTDIFFUSE_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_SPOTDIFFUSE_PROP_COLOR
 D2D1_VECTOR_3F
{1.0f, 1.0f, 1.0f}
 The color of the incoming light. This property is exposed as a Vector 3 (R, G, B) and used to compute LR, LG, LB.
KernelUnitLength
D2D1_SPOTDIFFUSE_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 (DIPs/Kernel Unit). The effect uses bilinear interpolation to scale the bitmap to match size of kernel elements.
ScaleMode
D2D1_SPOTDIFFUSE_PROP_SCALE_MODE
 D2D1_SPOTDIFFUSE_SCALE_MODE
D2D1_SPOTDIFFUSE_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. See Scale modes for more info.

Scale modes

Enumeration Description
D2D1_SPOTDIFFUSE_SCALE_MODE_NEAREST_NEIGHBOR Samples the nearest single point and uses that. This mode uses less processing time, but outputs the lowest quality image.
D2D1_SPOTDIFFUSE_SCALE_MODE_LINEAR Uses a four point sample and linear interpolation. This mode outputs a higher quality image than nearest neighbor.
D2D1_SPOTDIFFUSE_SCALE_MODE_CUBIC Uses a 16 sample cubic kernel for interpolation. This mode uses the most processing time, but outputs a higher quality image.
D2D1_SPOTDIFFUSE_SCALE_MODE_MULTI_SAMPLE_LINEAR Uses 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_SPOTDIFFUSE_SCALE_MODE_ANISOTROPIC Uses anisotropic filtering to sample a pattern according to the transformed shape of the bitmap.
D2D1_SPOTDIFFUSE_SCALE_MODE_HIGH_QUALITY_CUBIC Uses 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_SPOTDIFFUSE_SCALE_MODE_LINEAR.

Requirements

Requirement Value
Minimum supported client Windows 8 and Platform Update for Windows 7 [desktop apps | Windows Store apps]
Minimum supported server Windows 8 and Platform Update for Windows 7 [desktop apps | Windows Store apps]
Header d2d1effects.h
Library d2d1.lib, dxguid.lib

ID2D1Effect