allow gaussian volume without blendMinMax

src/mol-math/geometry/gaussian-density/gpu.ts

@@ -120,7 +120,7 @@ type _GaussianDensityTextureData = {
 
 function calcGaussianDensityTexture2d(webgl: WebGLContext, position: PositionData, box: Box3D, radius: (index: number) => number, powerOfTwo: boolean, props: GaussianDensityProps, texture?: Texture): _GaussianDensityTextureData {
     // console.log('2d');
-    const { gl, resources, state, extensions: { colorBufferFloat, textureFloat, colorBufferHalfFloat, textureHalfFloat } } = webgl;
+    const { gl, resources, state, extensions: { colorBufferFloat, textureFloat, colorBufferHalfFloat, textureHalfFloat, blendMinMax } } = webgl;
     const { smoothness, resolution } = props;
 
     const { drawCount, positions, radii, groups, scale, expandedBox, dim, maxRadius } = prepareGaussianDensityData(position, box, radius, props);
@@ -190,11 +190,13 @@ function calcGaussianDensityTexture2d(webgl: WebGLContext, position: PositionDat
     setupDensityRendering(webgl, renderable);
     render(texture, true);
 
-    setupMinDistanceRendering(webgl, renderable);
-    render(minDistTex, true);
+    if (blendMinMax) {
+        setupMinDistanceRendering(webgl, renderable);
+        render(minDistTex, true);
 
-    setupGroupIdRendering(webgl, renderable);
-    render(texture, false);
+        setupGroupIdRendering(webgl, renderable);
+        render(texture, false);
+    }
 
     // printTexture(webgl, minDistTex, 0.75);
 

src/mol-repr/structure/visual/gaussian-density-volume.ts

@@ -73,8 +73,11 @@ export function GaussianDensityVolumeVisual(materialId: number): ComplexVisual<G
 
 async function createUnitsGaussianDensityVolume(ctx: VisualContext, unit: Unit, structure: Structure, theme: Theme, props: GaussianDensityProps, directVolume?: DirectVolume): Promise<DirectVolume> {
     const { runtime, webgl } = ctx;
-    if (!webgl || !webgl.extensions.blendMinMax) {
-        throw new Error('GaussianDensityVolume requires `webgl` and `blendMinMax` extension');
+    if (!webgl) {
+        // gpu gaussian density also needs blendMinMax but there is no fallback here so
+        // we allow it here with the results that there is no group id assignment and
+        // hence no group-based coloring or picking
+        throw new Error('GaussianDensityVolume requires `webgl`');
     }
 
     const p = { ...props, useGpu: true };