58 lines
2 KiB
Text
58 lines
2 KiB
Text
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const float V2_UNIT_STEPS = 1024.0;
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const float V2_MIN = -8192.0;
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const float V2_MAX = 8191.0;
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const float V2_DF = 255.0 / V2_UNIT_STEPS;
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float decode_height_from_rgb8_unorm_2(vec3 c) {
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return (c.r * 0.25 + c.g * 64.0 + c.b * 16384.0) * (4.0 * V2_DF) + V2_MIN;
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}
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vec3 encode_height_to_rgb8_unorm_2(float h) {
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// TODO Check if this has float precision issues
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// TODO Modulo operator might be a performance/compatibility issue
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h -= V2_MIN;
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int i = int(h * V2_UNIT_STEPS);
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int r = i % 256;
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int g = (i / 256) % 256;
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int b = i / 65536;
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return vec3(float(r), float(g), float(b)) / 255.0;
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}
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float decode_height_from_rgb8_unorm(vec3 c) {
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return decode_height_from_rgb8_unorm_2(c);
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}
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vec3 encode_height_to_rgb8_unorm(float h) {
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return encode_height_to_rgb8_unorm_2(h);
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}
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// TODO Remove for now?
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// Bilinear filtering appears to work well enough without doing this.
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// There are some artifacts, but we could easily live with them,
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// and I suspect they could be easy to patch somehow in the encoding/decoding.
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//
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// In case bilinear filtering is required.
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// This is slower than if we had a native float format.
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// Unfortunately, Godot 4 removed support for 2D HDR viewports. They were used
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// to edit this format natively. Using compute shaders would force users to
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// have Vulkan. So we had to downgrade performance a bit using a technique from the GLES2 era...
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float sample_height_bilinear_rgb8_unorm(sampler2D heightmap, vec2 uv) {
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vec2 ts = vec2(textureSize(heightmap, 0));
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vec2 p00f = uv * ts;
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ivec2 p00 = ivec2(p00f);
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vec3 s00 = texelFetch(heightmap, p00, 0).rgb;
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vec3 s10 = texelFetch(heightmap, p00 + ivec2(1, 0), 0).rgb;
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vec3 s01 = texelFetch(heightmap, p00 + ivec2(0, 1), 0).rgb;
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vec3 s11 = texelFetch(heightmap, p00 + ivec2(1, 1), 0).rgb;
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float h00 = decode_height_from_rgb8_unorm(s00);
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float h10 = decode_height_from_rgb8_unorm(s10);
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float h01 = decode_height_from_rgb8_unorm(s01);
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float h11 = decode_height_from_rgb8_unorm(s11);
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vec2 f = p00f - vec2(p00);
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return mix(mix(h00, h10, f.x), mix(h01, h11, f.x), f.y);
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}
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