Min & Max Values for CreateGroundFromHeightMap

3D_Wave_Design · April 29, 2020, 7:17pm

Hello all,

I hope everyone is staying safe these days! I’ve been playing around the CreateGroundFromHeightMap function to create 3D models based on DEM rasters. In QGIS I’m able to see the height range, as seen in this picture, but when these values are put into the function’s minHeight / maxHeight parameters the model seems vertically stretched more than it should.

I was wondering how Babylon’s ground from heightmap function works with these values, so I can maintain as much accuracy as possible.

Thanks for your time!

sebavan · April 29, 2020, 7:43pm

It is all in here: Babylon.js/groundBuilder.ts at master · BabylonJS/Babylon.js · GitHub

and mainly here:

github.com

BabylonJS/Babylon.js/blob/master/src/Meshes/Builders/groundBuilder.ts#L186


        r = 1.0 - r;

        g = 1.0 - g;

        b = 1.0 - b;

    }



    var gradient = r * filter.r + g * filter.g + b * filter.b;



    // If our alpha channel is not within our filter then we will assign a 'special' height

    // Then when building the indices, we will ignore any vertex that is using the special height

    if (a >= alphaFilter) {

        position.y = options.minHeight + (options.maxHeight - options.minHeight) * gradient;

    }

    else {

        position.y = options.minHeight - Epsilon; // We can't have a height below minHeight, normally.

    }



    // Add  vertex

    positions.push(position.x, position.y, position.z);

    normals.push(0, 0, 0);

    uvs.push(col / options.subdivisions, 1.0 - row / options.subdivisions);

}

maybe that is the computation of the gradient using all colors of the textures ?

3D_Wave_Design · April 29, 2020, 7:56pm

I think I prematurely clicked “solution” haha. Definitely a point in the right direction. I’ll have to wrap my head around this and try again. Thanks for the resource!

3D_Wave_Design · April 30, 2020, 2:04pm

@sebavan So I believe the issue was do to incorrect scaling of the mesh plane. Looking good now! Thanks for linking the GitHub resource; I have a better understanding how the RGB values are handled.

Take care!

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Min & Max Values for CreateGroundFromHeightMap

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