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picking

Provides support for color-based picking.

The picking modules supports picking and highlighting for both instanced and non-instanced data:

  • pick a specific instance in an instanced draw call
  • highlight all fragments of an instance based on its picking color
  • pick "group of primitives" with the same picking color in non-instanced draw-calls
  • highlight "group of primitives" with the same picking color in non-instanced draw-calls

Color based picking lets the application draw a primitive with a color that can later be used to index this specific primitive.

Highlighting allows application to specify a picking color corresponding to an object that need to be highlighted and the highlight color to be used.

Usage

In your vertex shader, your inform the picking module what object we are currently rendering by supplying a picking color, perhaps from an attribute.

attribute vec3 aPickingColor;
main() {
picking_setPickingColor(aPickingColor);
...
}

In your fragment shader, you simply apply (call) the picking_filterColor filter function at the very end of the shader. This will return the normal color, or the highlight color, or the picking color, as appropriate.

main() {
gl_FragColor = ...
gl_FragColor = picking_filterPickingColor(gl_FragColor);
}

In your fragment shader, you simply apply (call) the picking_filterPickingColor filter function at the very end of the shader. This will return the normal color, or the highlight color, or the picking color, as appropriate.

main() {
gl_FragColor = ...
gl_FragColor = picking_filterPickingColor(gl_FragColor);
}

If highlighting is not needed, you simply apply (call) the picking_filterPickingColor filter function at the very end of the shader. This will return the normal color or the picking color, as appropriate.

main() {
gl_FragColor = ...
gl_FragColor = picking_filterPickingColor(gl_FragColor);
}

If you would like to apply the highlight color to the currently selected element call picking_filterHighlightColor before calling picking_filterPickingColor. You can also apply other filters on the non-picking color (vertex or highlight color) by placing those instruction between these two function calls.

main() {
gl_FragColor = ...
gl_FragColor = picking_filterHighlightColor(gl_FragColor);
... apply any filters on gl_FragColor ...
gl_FragColor = picking_filterPickingColor(gl_FragColor);
}

JavaScript Functions

getUniforms()

getUniforms() takes an object with key/value pairs, returns an object with key/value pairs representing the uniforms that the picking module shaders need.

Uniforms for the picking module, which renders picking colors and highlighted item. When active, renders picking colors, assumed to be rendered to off-screen "picking" buffer. When inactive, renders normal colors, with the exception of selected object which is rendered with highlight

SettingDescription
isActive?: booleanWhether in picking or normal rendering (+highlighting) mode
isAttribute: booleanSet to true when picking an attribute value instead of object index
useFloatColors?: booleanColor range 0-1 or 0-255
isHighlightActive?: booleanDo we have a highlighted item?
highlightedObjectColor?: NumberArraySet to a picking color to visually highlight that item
highlightColor?: NumberArrayColor of visual highlight of "selected" item
  • isActive - When true, renders picking colors. Set when rendering to off-screen "picking" buffer. When false, renders normal colors, with the exception of selected object which is rendered with highlight

Vertex Shader Functions

picking_setPickingColor()

void picking_setPickingColor(vec3 pickingColor)

Sets the color that will be returned by the fragment shader if color based picking is enabled. Typically set from a pickingColor uniform or a pickingColors attribute (e.g. when using instanced rendering, to identify the actual instance that was picked).

picking_setPickingAttribute

Sets the attribute value that needs to be picked.

void picking_setPickingAttribute(float value) void picking_setPickingAttribute(vec2 value) void picking_setPickingAttribute(vec3 value)

Fragment Shader Functions

picking_filterColor

fn picking_filterColor(color: vec4<f32>) -> vec4<f32>
vec4 picking_filterColor(vec4 color)
Picking EnabledItem HighlightedReturned color
Returns picking color (representing index of this color)
Returns the current highlight color (to show this item as "selected")
returns the original color (unmodified color argument)

picking_filterPickingColor()

vec4 picking_filterPickingColor(vec4 color)

If picking active, returns the current vertex's picking color set by picking_setPickingColor, otherwise returns its argument unmodified.

Returns picking highlight color if the pixel belongs to currently selected model, otherwise returns its argument unmodified.

picking_filterPickingColor()

vec4 picking_filterPickingColor(vec4 color)

If picking active, returns the current vertex's picking color set by picking_setPickingColor, otherwise returns its argument unmodified.

Remarks

  • It is recommended that picking_filterPickingColor() is called last in a fragment shader, as the picking color (returned when picking is enabled) must not be modified in any way (and alpha must remain 1) or picking results will not be correct.