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Update per mdn webgl recommendations #9474

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Apr 1, 2020
Merged

Update per mdn webgl recommendations #9474

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30b39cd
Update per mdn webgl recommendations
karimnaaji Mar 27, 2020
f4d7d22
Add heatmap layer to release testing
karimnaaji Mar 31, 2020
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2 changes: 2 additions & 0 deletions src/gl/context.js
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Original file line number Diff line number Diff line change
Expand Up @@ -63,6 +63,7 @@ class Context {
extTextureFilterAnisotropic: any;
extTextureFilterAnisotropicMax: any;
extTextureHalfFloat: any;
extRenderToTextureHalfFloat: any;
extTimerQuery: any;

constructor(gl: WebGLRenderingContext) {
Expand Down Expand Up @@ -113,6 +114,7 @@ class Context {
this.extTextureHalfFloat = gl.getExtension('OES_texture_half_float');
if (this.extTextureHalfFloat) {
gl.getExtension('OES_texture_half_float_linear');
this.extRenderToTextureHalfFloat = gl.getExtension('EXT_color_buffer_half_float');
}

this.extTimerQuery = gl.getExtension('EXT_disjoint_timer_query');
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13 changes: 3 additions & 10 deletions src/render/draw_heatmap.js
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Expand Up @@ -100,17 +100,10 @@ function bindFramebuffer(context, painter, layer) {
function bindTextureToFramebuffer(context, painter, texture, fbo) {
const gl = context.gl;
// Use the higher precision half-float texture where available (producing much smoother looking heatmaps);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, painter.width / 4, painter.height / 4, 0, gl.RGBA,
context.extTextureHalfFloat ? context.extTextureHalfFloat.HALF_FLOAT_OES : gl.UNSIGNED_BYTE, null);

// Otherwise, fall back to a low precision texture
const internalFormat = context.extRenderToTextureHalfFloat ? context.extTextureHalfFloat.HALF_FLOAT_OES : gl.UNSIGNED_BYTE;
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, painter.width / 4, painter.height / 4, 0, gl.RGBA, internalFormat, null);
fbo.colorAttachment.set(texture);

// If using half-float texture as a render target is not supported, fall back to a low precision texture
if (context.extTextureHalfFloat && gl.checkFramebufferStatus(gl.FRAMEBUFFER) !== gl.FRAMEBUFFER_COMPLETE) {
context.extTextureHalfFloat = null;
fbo.colorAttachment.setDirty();
bindTextureToFramebuffer(context, painter, texture, fbo);
}
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The reason why it was implemented this way is because of this excerpt from the EXT_color_buffer_half_float spec:

Although it is expected that all implementations supporting this extension support rendering to at least one HALF_FLOAT_OES format, applications must check framebuffer completeness to determine which formats are supported.

So basically it says that the extension being enabled doesn't guarantee that writing to a half-float framebuffer will succeed. I don't know how often this situation happens in practice (maybe never?), but we should be aware of the risk of this PR breaking heatmaps for some users (where it won't fall back to low precision properly).

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I think that's a recommendation for the desktop GL extension GL_EXT_color_buffer_half_float which gets exposed a bit differently for the webgl one.

For example, here are the thorough tests that chromium goes through before exposing it to the WebGL API, and does the completeness check. I have not seen similar suggestion in mdn or the webgl spec reference.

I tested this last friday on both a iphone 6 and mali-t760 (galaxy s3) which don't report supporting this extension, and fallback appropriately. I would be ok in leaving it as is, but with these concerns we could leave an assert probe and see whether it gets triggered until the beta completes?

}

function renderTextureToMap(painter, layer) {
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3 changes: 3 additions & 0 deletions src/render/program.js
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Expand Up @@ -76,6 +76,9 @@ class Program<Us: UniformBindings> {
gl.linkProgram(this.program);
assert(gl.getProgramParameter(this.program, gl.LINK_STATUS), (gl.getProgramInfoLog(this.program): any));

gl.deleteShader(vertexShader);
gl.deleteShader(fragmentShader);

this.numAttributes = gl.getProgramParameter(this.program, gl.ACTIVE_ATTRIBUTES);

this.attributes = {};
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