godot/drivers/gles3/shaders/ssao.glsl
2016-12-04 12:45:30 -03:00

248 lines
7.4 KiB
GLSL

[vertex]
layout(location=0) in highp vec4 vertex_attrib;
void main() {
gl_Position = vertex_attrib;
gl_Position.z=1.0;
}
[fragment]
#define NUM_SAMPLES (11)
// If using depth mip levels, the log of the maximum pixel offset before we need to switch to a lower
// miplevel to maintain reasonable spatial locality in the cache
// If this number is too small (< 3), too many taps will land in the same pixel, and we'll get bad variance that manifests as flashing.
// If it is too high (> 5), we'll get bad performance because we're not using the MIP levels effectively
#define LOG_MAX_OFFSET (3)
// This must be less than or equal to the MAX_MIP_LEVEL defined in SSAO.cpp
#define MAX_MIP_LEVEL (4)
// This is the number of turns around the circle that the spiral pattern makes. This should be prime to prevent
// taps from lining up. This particular choice was tuned for NUM_SAMPLES == 9
#define NUM_SPIRAL_TURNS (7)
uniform sampler2D source_depth; //texunit:0
uniform usampler2D source_depth_mipmaps; //texunit:1
uniform sampler2D source_normal; //texunit:2
uniform ivec2 screen_size;
uniform float camera_z_far;
uniform float camera_z_near;
uniform float intensity_div_r6;
uniform float radius;
#ifdef ENABLE_RADIUS2
uniform float intensity_div_r62;
uniform float radius2;
#endif
uniform float bias;
uniform float proj_scale;
layout(location = 0) out float visibility;
uniform vec4 proj_info;
vec3 reconstructCSPosition(vec2 S, float z) {
return vec3((S.xy * proj_info.xy + proj_info.zw) * z, z);
}
vec3 getPosition(ivec2 ssP) {
vec3 P;
P.z = texelFetch(source_depth, ssP, 0).r;
P.z = P.z * 2.0 - 1.0;
P.z = 2.0 * camera_z_near * camera_z_far / (camera_z_far + camera_z_near - P.z * (camera_z_far - camera_z_near));
P.z = -P.z;
// Offset to pixel center
P = reconstructCSPosition(vec2(ssP) + vec2(0.5), P.z);
return P;
}
/** Reconstructs screen-space unit normal from screen-space position */
vec3 reconstructCSFaceNormal(vec3 C) {
return normalize(cross(dFdy(C), dFdx(C)));
}
/** Returns a unit vector and a screen-space radius for the tap on a unit disk (the caller should scale by the actual disk radius) */
vec2 tapLocation(int sampleNumber, float spinAngle, out float ssR){
// Radius relative to ssR
float alpha = float(sampleNumber + 0.5) * (1.0 / NUM_SAMPLES);
float angle = alpha * (NUM_SPIRAL_TURNS * 6.28) + spinAngle;
ssR = alpha;
return vec2(cos(angle), sin(angle));
}
/** Read the camera-space position of the point at screen-space pixel ssP + unitOffset * ssR. Assumes length(unitOffset) == 1 */
vec3 getOffsetPosition(ivec2 ssC, vec2 unitOffset, float ssR) {
// Derivation:
// mipLevel = floor(log(ssR / MAX_OFFSET));
int mipLevel = clamp(int(floor(log2(ssR))) - LOG_MAX_OFFSET, 0, MAX_MIP_LEVEL);
ivec2 ssP = ivec2(ssR * unitOffset) + ssC;
vec3 P;
// We need to divide by 2^mipLevel to read the appropriately scaled coordinate from a MIP-map.
// Manually clamp to the texture size because texelFetch bypasses the texture unit
ivec2 mipP = clamp(ssP >> mipLevel, ivec2(0), (screen_size >> mipLevel) - ivec2(1));
if (mipLevel < 1) {
//read from depth buffer
P.z = texelFetch(source_depth, mipP, 0).r;
P.z = P.z * 2.0 - 1.0;
P.z = 2.0 * camera_z_near * camera_z_far / (camera_z_far + camera_z_near - P.z * (camera_z_far - camera_z_near));
P.z = -P.z;
} else {
//read from mipmaps
uint d = texelFetch(source_depth_mipmaps, mipP, mipLevel-1).r;
P.z = -(float(d)/65535.0)*camera_z_far;
}
// Offset to pixel center
P = reconstructCSPosition(vec2(ssP) + vec2(0.5), P.z);
return P;
}
/** Compute the occlusion due to sample with index \a i about the pixel at \a ssC that corresponds
to camera-space point \a C with unit normal \a n_C, using maximum screen-space sampling radius \a ssDiskRadius
Note that units of H() in the HPG12 paper are meters, not
unitless. The whole falloff/sampling function is therefore
unitless. In this implementation, we factor out (9 / radius).
Four versions of the falloff function are implemented below
*/
float sampleAO(in ivec2 ssC, in vec3 C, in vec3 n_C, in float ssDiskRadius,in float p_radius, in int tapIndex, in float randomPatternRotationAngle) {
// Offset on the unit disk, spun for this pixel
float ssR;
vec2 unitOffset = tapLocation(tapIndex, randomPatternRotationAngle, ssR);
ssR *= ssDiskRadius;
// The occluding point in camera space
vec3 Q = getOffsetPosition(ssC, unitOffset, ssR);
vec3 v = Q - C;
float vv = dot(v, v);
float vn = dot(v, n_C);
const float epsilon = 0.01;
float radius2 = p_radius*p_radius;
// A: From the HPG12 paper
// Note large epsilon to avoid overdarkening within cracks
//return float(vv < radius2) * max((vn - bias) / (epsilon + vv), 0.0) * radius2 * 0.6;
// B: Smoother transition to zero (lowers contrast, smoothing out corners). [Recommended]
float f=max(radius2 - vv, 0.0);
return f * f * f * max((vn - bias) / (epsilon + vv), 0.0);
// C: Medium contrast (which looks better at high radii), no division. Note that the
// contribution still falls off with radius^2, but we've adjusted the rate in a way that is
// more computationally efficient and happens to be aesthetically pleasing.
// return 4.0 * max(1.0 - vv * invRadius2, 0.0) * max(vn - bias, 0.0);
// D: Low contrast, no division operation
// return 2.0 * float(vv < radius * radius) * max(vn - bias, 0.0);
}
void main() {
// Pixel being shaded
ivec2 ssC = ivec2(gl_FragCoord.xy);
// World space point being shaded
vec3 C = getPosition(ssC);
/* if (C.z <= -camera_z_far*0.999) {
// We're on the skybox
visibility=1.0;
return;
}*/
//visibility=-C.z/camera_z_far;
//return;
//vec3 n_C = texelFetch(source_normal,ssC,0).rgb * 2.0 - 1.0;
vec3 n_C = reconstructCSFaceNormal(C);
n_C = -n_C;
// Hash function used in the HPG12 AlchemyAO paper
float randomPatternRotationAngle = (3 * ssC.x ^ ssC.y + ssC.x * ssC.y) * 10;
// Reconstruct normals from positions. These will lead to 1-pixel black lines
// at depth discontinuities, however the blur will wipe those out so they are not visible
// in the final image.
// Choose the screen-space sample radius
// proportional to the projected area of the sphere
float ssDiskRadius = -proj_scale * radius / C.z;
float sum = 0.0;
for (int i = 0; i < NUM_SAMPLES; ++i) {
sum += sampleAO(ssC, C, n_C, ssDiskRadius, radius,i, randomPatternRotationAngle);
}
float A = max(0.0, 1.0 - sum * intensity_div_r6 * (5.0 / NUM_SAMPLES));
#ifdef ENABLE_RADIUS2
//go again for radius2
randomPatternRotationAngle = (5 * ssC.x ^ ssC.y + ssC.x * ssC.y) * 11;
// Reconstruct normals from positions. These will lead to 1-pixel black lines
// at depth discontinuities, however the blur will wipe those out so they are not visible
// in the final image.
// Choose the screen-space sample radius
// proportional to the projected area of the sphere
ssDiskRadius = -proj_scale * radius2 / C.z;
sum = 0.0;
for (int i = 0; i < NUM_SAMPLES; ++i) {
sum += sampleAO(ssC, C, n_C, ssDiskRadius,radius2, i, randomPatternRotationAngle);
}
A= min(A,max(0.0, 1.0 - sum * intensity_div_r62 * (5.0 / NUM_SAMPLES)));
#endif
// Bilateral box-filter over a quad for free, respecting depth edges
// (the difference that this makes is subtle)
if (abs(dFdx(C.z)) < 0.02) {
A -= dFdx(A) * ((ssC.x & 1) - 0.5);
}
if (abs(dFdy(C.z)) < 0.02) {
A -= dFdy(A) * ((ssC.y & 1) - 0.5);
}
visibility = A;
}