Switch from automatic to manual depth testing for billboards #12821
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There was a problem hiding this comment. I would recommend reviewing the VS before the FS. |
| Original file line number | Diff line number | Diff line change | ||||||
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| @@ -1,4 +1,6 @@ | ||||||||
| uniform sampler2D u_atlas; | ||||||||
| uniform float u_coarseDepthTestDistance; | ||||||||
| uniform float u_threePointDepthTestDistance; | ||||||||
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| #ifdef VECTOR_TILE | ||||||||
| uniform vec4 u_highlightColor; | ||||||||
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@@ -14,18 +16,33 @@ in vec4 v_outlineColor; | |||||||
| in float v_outlineWidth; | ||||||||
| #endif | ||||||||
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| in vec4 v_compressed; // x: eyeDepth, y: applyTranslate & enableDepthCheck, z: dimensions, w: imageSize | ||||||||
| const float SHIFT_LEFT1 = 2.0; | ||||||||
| const float SHIFT_RIGHT1 = 1.0 / 2.0; | ||||||||
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There was a problem hiding this comment. These changes, among several others in this PR, are just moving variables outside of macro checks. These used to be only used if |
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| #ifdef FS_THREE_POINT_DEPTH_CHECK | ||||||||
| in vec4 v_textureCoordinateBounds; // the min and max x and y values for the texture coordinates | ||||||||
| in vec4 v_originTextureCoordinateAndTranslate; // texture coordinate at the origin, billboard translate (used for label glyphs) | ||||||||
| in mat2 v_rotationMatrix; | ||||||||
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| const float SHIFT_LEFT12 = 4096.0; | ||||||||
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| const float SHIFT_RIGHT12 = 1.0 / 4096.0; | ||||||||
| #endif | ||||||||
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| float getGlobeDepthAtCoords(vec2 st) | ||||||||
| { | ||||||||
| float logDepthOrDepth = czm_unpackDepth(texture(czm_globeDepthTexture, st)); | ||||||||
| if (logDepthOrDepth == 0.0) | ||||||||
| { | ||||||||
| return 0.0; // not on the globe | ||||||||
| } | ||||||||
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There was a problem hiding this comment. This isn't a new function, really. It just breaks the old |
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| vec4 eyeCoordinate = czm_windowToEyeCoordinates(gl_FragCoord.xy, logDepthOrDepth); | ||||||||
| return eyeCoordinate.z / eyeCoordinate.w; | ||||||||
| } | ||||||||
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| #ifdef FS_THREE_POINT_DEPTH_CHECK | ||||||||
| float getGlobeDepth(vec2 adjustedST, vec2 depthLookupST, bool applyTranslate, vec2 dimensions, vec2 imageSize) | ||||||||
| { | ||||||||
| vec2 lookupVector = imageSize * (depthLookupST - adjustedST); | ||||||||
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@@ -42,19 +59,10 @@ float getGlobeDepth(vec2 adjustedST, vec2 depthLookupST, bool applyTranslate, ve | |||||||
| } | ||||||||
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| vec2 st = ((lookupVector - translation + labelOffset) + gl_FragCoord.xy) / czm_viewport.zw; | ||||||||
| return getGlobeDepthAtCoords(st); | ||||||||
| } | ||||||||
| #endif | ||||||||
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| #ifdef SDF | ||||||||
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| // Get the distance from the edge of a glyph at a given position sampling an SDF texture. | ||||||||
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@@ -85,10 +93,89 @@ vec4 getSDFColor(vec2 position, float outlineWidth, vec4 outlineColor, float smo | |||||||
| } | ||||||||
| #endif | ||||||||
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| #ifdef FS_THREE_POINT_DEPTH_CHECK | ||||||||
| void doThreePointDepthTest(float eyeDepth, bool applyTranslate) { | ||||||||
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| if (eyeDepth < -u_threePointDepthTestDistance) return; | ||||||||
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There was a problem hiding this comment. Code style is to always use There was a problem hiding this comment. The rest of this file has a few other occurrences. Please do a pass. There was a problem hiding this comment. Will do. Usually prettier catches me on those but I guess not in shader code! There was a problem hiding this comment. Fair! I'd love to eventually get our shader tooling up to par with what we have for JS. |
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| float temp = v_compressed.z; | ||||||||
| temp = temp * SHIFT_RIGHT12; | ||||||||
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| vec2 dimensions; | ||||||||
| dimensions.y = (temp - floor(temp)) * SHIFT_LEFT12; | ||||||||
| dimensions.x = floor(temp); | ||||||||
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| temp = v_compressed.w; | ||||||||
| temp = temp * SHIFT_RIGHT12; | ||||||||
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| vec2 imageSize; | ||||||||
| imageSize.y = (temp - floor(temp)) * SHIFT_LEFT12; | ||||||||
| imageSize.x = floor(temp); | ||||||||
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| vec2 adjustedST = v_textureCoordinates - v_textureCoordinateBounds.xy; | ||||||||
| adjustedST = adjustedST / vec2(v_textureCoordinateBounds.z - v_textureCoordinateBounds.x, v_textureCoordinateBounds.w - v_textureCoordinateBounds.y); | ||||||||
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| float epsilonEyeDepth = v_compressed.x + czm_epsilon1; | ||||||||
| float globeDepth1 = getGlobeDepth(adjustedST, v_originTextureCoordinateAndTranslate.xy, applyTranslate, dimensions, imageSize); | ||||||||
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| // negative values go into the screen | ||||||||
| if (globeDepth1 == 0.0 || globeDepth1 < epsilonEyeDepth) return; | ||||||||
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| float globeDepth2 = getGlobeDepth(adjustedST, vec2(0.0, 1.0), applyTranslate, dimensions, imageSize); // top left corner | ||||||||
| if (globeDepth2 == 0.0 || globeDepth2 < epsilonEyeDepth) return; | ||||||||
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| float globeDepth3 = getGlobeDepth(adjustedST, vec2(1.0, 1.0), applyTranslate, dimensions, imageSize); // top right corner | ||||||||
| if (globeDepth3 == 0.0 || globeDepth3 < epsilonEyeDepth) return; | ||||||||
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| // All three key points are occluded, discard the fragment (and by extension the entire billboard) | ||||||||
| discard; | ||||||||
| } | ||||||||
| #endif | ||||||||
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| void doDepthTest() { | ||||||||
| float temp = v_compressed.y; | ||||||||
| temp = temp * SHIFT_RIGHT1; | ||||||||
| float temp2 = (temp - floor(temp)) * SHIFT_LEFT1; | ||||||||
| bool enableDepthCheck = temp2 != 0.0; | ||||||||
| if (!enableDepthCheck) return; | ||||||||
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| float eyeDepth = v_compressed.x; | ||||||||
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| #ifdef FS_THREE_POINT_DEPTH_CHECK | ||||||||
| // If the billboard is clamped to the ground and within a given distance, we do a 3-point depth test. This test is performed in the vertex shader, unless | ||||||||
| // vertex texture sampling is not supported, in which case we do it here. | ||||||||
| bool applyTranslate = floor(temp) != 0.0; | ||||||||
| doThreePointDepthTest(eyeDepth, applyTranslate); | ||||||||
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| #elif defined(VS_THREE_POINT_DEPTH_CHECK) | ||||||||
| // Since discarding vertices is not possible, the vertex shader sets eyeDepth to 0 to indicate the depth test failed. Apply the discard here. | ||||||||
| if (eyeDepth > -u_threePointDepthTestDistance) { | ||||||||
| if (eyeDepth == 0.0) { | ||||||||
| discard; | ||||||||
| } | ||||||||
| return; | ||||||||
| } | ||||||||
| #endif | ||||||||
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| // Automatic depth testing of billboards is disabled (@see BillboardCollection#update). | ||||||||
| // Instead, we do one of two types of manual depth tests (potentially in addition to the test above), depending on the camera's distance to the billboard fragment. | ||||||||
| // If we're far away, we just compare against a flat, camera-facing depth-plane at the ellipsoid's center. | ||||||||
| // If we're close, we compare against the globe depth texture (which includes depth from the 3D tile pass). | ||||||||
| vec2 fragSt = gl_FragCoord.xy / czm_viewport.zw; | ||||||||
| float globeDepth = getGlobeDepthAtCoords(fragSt); | ||||||||
| if (globeDepth == 0.0) return; // Not on globe | ||||||||
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| float distanceToEllipsoidCenter = -length(czm_viewerPositionWC); // depth is negative by convention | ||||||||
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There was a problem hiding this comment. Sorry, didn't notice this until now— Does Out of curiosity, I was able to do a quick test and get a fallback depth based on computing the depth of the intersection with the ellipsoid (see Kevin's horizon culling blog post for more info) through each vertex. I pushed up my patch to It seems to be working pretty well for mid-level horizon views as well as at the global scale:
And it seems to be working well for 3D Tiles as well, so in that branch I was able to remove the custom Thoughts? There was a problem hiding this comment. So, I do think Separately (but perhaps making the above irrelevant) I didn't even consider horizon culling, and your images of it look aesthetically better to me. I think we should take your patch. (I wonder- was horizon culling being done on billboards before this PR? I think not, right?) There was a problem hiding this comment. Re: mars and moon, I was thinking about removing the depth distance check after this PR, even as I was writing the Mars sandcastle. I'm eager for that because I don't think that stop gap worked particularly well. There was a problem hiding this comment.
Thanks for the explanation! That makes sense in retrospect.
Not to my knowledge, no. There was a problem hiding this comment.
👍 I'll go ahead and merge this PR then open a new one with my patch for your review. There was a problem hiding this comment. After more thought, I think my above comment was wrong (well, what I said about position vs. distance is true, but the conclusion is wrong). My code was just comparing two distances (camera-to-globe-center, to camera-to-billboard). But really it should have been projecting the camera-to-billboard vector onto the camera-to-globe vector, and comparing the length of the projected vector to the camera-to-globe distance. And, for that math, the reference frames must be the same - so I think you were right to be confused. In any case, the horizon culling approach will fix that and be more precise. Just wanted to clarify for posterity, and so I'm not gaslighting anyone :) |
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| float testDistance = (eyeDepth > -u_coarseDepthTestDistance) ? globeDepth : distanceToEllipsoidCenter; | ||||||||
| if (eyeDepth < testDistance) { | ||||||||
| discard; | ||||||||
| } | ||||||||
| } | ||||||||
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| void main() | ||||||||
| { | ||||||||
| if (v_splitDirection < 0.0 && gl_FragCoord.x > czm_splitPosition) discard; | ||||||||
| if (v_splitDirection > 0.0 && gl_FragCoord.x < czm_splitPosition) discard; | ||||||||
| doDepthTest(); | ||||||||
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| vec4 color = texture(u_atlas, v_textureCoordinates); | ||||||||
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@@ -158,51 +245,4 @@ void main() | |||||||
| #ifdef LOG_DEPTH | ||||||||
| czm_writeLogDepth(); | ||||||||
| #endif | ||||||||
| } | ||||||||
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This is what I mentioned above. Removing in favor of always using a 5km distance.