Fix for queryRenderedFeatures on fill-extrusions where a large part of the extrusion is behind the camera #10428
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… behind the camera
| out[2] = (m[2] * x + m[6] * y + m[10] * z + m[14]) / w; | ||
| return out; | ||
| } | ||
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I don't think you need a specialized transform function for this purpose. You could use a generic matrix multiplication instead (m44 * m41) and divide the resulting vector by w afterwards. Something like this:
const vec = mul(m, [a0, a1, a2, 1]);
vec /= max(vec[3], 0.00001);
| @@ -232,12 +231,12 @@ function projectExtrusion2D(geometry: Array<Array<Point>>, zBase: number, zTop: | |||
| const baseX = sX + baseXZ; | |||
| const baseY = sY + baseYZ; | |||
| const baseZ = sZ + baseZZ; | |||
| const baseW = sW + baseWZ; | |||
| const baseW = Math.max(sW + baseWZ, 0.00001); | |||
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A comment or link to this issue might be helpful since the reason for this line may not be obvious.
Also, can baseW be negative but not close to zero? Just checking since it's not clear to me what this would compute if that were the case. For example, to avoid zero without otherwise changing the magnitude or sign of the number: Math.sign(sW + baseWZ) * Math.max(Math.abs(sW + baseWZ), 0.00001);.
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(To at least be clear if I'm going to be pedantic, because it's homogeneous, the result would be exactly identical if all of the components were simply negated—unless the clamping didn't permit negative w in an exactly equivalent vector. Just wanted to be certain that it's an upstream guarantee that w is non-negative.)
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There is no issue for this. Discovered it while porting various QRF pr's to gl-native and needed a test, so also fixed it here. The PR and query tests should serve as plenty of documentation.
Also, can baseW be negative but not close to zero?
Yes, that is actually a major part of the issue
For example, to avoid zero without otherwise changing the magnitude or sign of the number
It's basically clamping, which serves us well in this case as we don't need the magnitude when w < 0.
For fill extrusions with parts behind the camera the projection was wrong resulting in false positives for query rendered features.
Before:
After:
Launch Checklist
@mapbox/gl-nativeif this PR includes shader changes or needs a native portmapbox-gl-jschangelog:<changelog>Fix queryRenderedFeatures for fill-extrusions partly behind the camera</changelog>