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addons/zylann.hterrain/shaders/include/heightmap.gdshaderinc

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+
+// Use functions from this file everywhere a heightmap is used,
+// so it is easy to track and change the format
+
+float sample_heightmap(sampler2D spl, vec2 pos) {
+	// RF
+	return texture(spl, pos).r;
+}
+
+vec4 encode_height_to_viewport(float h) {
+	//return vec4(encode_height_to_rgb8_unorm(h), 1.0);
+
+	// Encode regular floats into an assumed RGBA8 output color.
+	// This is used because Godot 4.0 doesn't support RF viewports,
+	// and the irony is, even if float viewports get supported, it's likely it will end up RGBAF,
+	// which is wasting bandwidth because we are only interested in R...
+	uint u = floatBitsToUint(h);
+	return vec4(
+		float((u >> 0u) & 255u),
+		float((u >> 8u) & 255u),
+		float((u >> 16u) & 255u),
+		float((u >> 24u) & 255u)
+	) / vec4(255.0);
+}
+
+float decode_height_from_viewport(vec4 c) {
+	uint u = uint(c.r * 255.0) 
+		| (uint(c.g * 255.0) << 8u) 
+		| (uint(c.b * 255.0) << 16u) 
+		| (uint(c.a * 255.0) << 24u);
+	return uintBitsToFloat(u);
+}
+
+float sample_height_from_viewport(sampler2D screen, vec2 uv) {
+	ivec2 ts = textureSize(screen, 0);
+	vec2 norm_to_px = vec2(ts);
+	
+	// Convert to pixels and apply a small offset so we interpolate from pixel centers
+	vec2 uv_px_f = uv * norm_to_px - vec2(0.5);
+
+	ivec2 uv_px = ivec2(uv_px_f);
+
+	// Get interpolation pixel positions
+	ivec2 p00 = uv_px;
+	ivec2 p10 = uv_px + ivec2(1, 0);
+	ivec2 p01 = uv_px + ivec2(0, 1);
+	ivec2 p11 = uv_px + ivec2(1, 1);
+
+	// Get pixels
+	vec4 c00 = texelFetch(screen, p00, 0);
+	vec4 c10 = texelFetch(screen, p10, 0);
+	vec4 c01 = texelFetch(screen, p01, 0);
+	vec4 c11 = texelFetch(screen, p11, 0);
+	
+	// Decode heights
+	float h00 = decode_height_from_viewport(c00);
+	float h10 = decode_height_from_viewport(c10);
+	float h01 = decode_height_from_viewport(c01);
+	float h11 = decode_height_from_viewport(c11);
+	
+	// Linear filter
+	vec2 f = fract(uv_px_f);
+	float h = mix(mix(h00, h10, f.x), mix(h01, h11, f.x), f.y);
+	
+	return h;
+}

addons/zylann.hterrain/shaders/include/heightmap.gdshaderinc.uid

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+uid://cejki3yhcmmd8

addons/zylann.hterrain/shaders/include/heightmap_rgb8_encoding.gdshaderinc

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

addons/zylann.hterrain/shaders/include/heightmap_rgb8_encoding.gdshaderinc.uid

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+uid://ctuxl7ko61ko0