[Bf-blender-cvs] [bc411ec] master: Cycles: Implement an area preserving parameterization sampling for area lamps
Sergey Sharybin
noreply at git.blender.org
Thu Oct 16 14:41:49 CEST 2014
Commit: bc411ec06ef429cc515313d9c87ec72a20c1e1ad
Author: Sergey Sharybin
Date: Fri Oct 10 19:24:12 2014 +0600
Branches: master
https://developer.blender.org/rBbc411ec06ef429cc515313d9c87ec72a20c1e1ad
Cycles: Implement an area preserving parameterization sampling for area lamps
Replace old code for area lamps which was more like incorrect with more correct
one using the following paper as a reference:
Carlos Urena et al.
An Area-Preserving Parametrization for Spherical Rectangles.
https://www.solidangle.com/research/egsr2013_spherical_rectangle.pdf
Implementation is straight from the paper, currently the rectangle constants are
calculated for each of the samples. Ideally we need to pre-calculate them.
Some comparison images are available there
http://wiki.blender.org/index.php/Dev:Ref/Release_Notes/2.73/Cycles
Reviewers: brecht, juicyfruit
Subscribers: dingto, ton
Differential Revision: https://developer.blender.org/D823
===================================================================
M intern/cycles/kernel/kernel_light.h
===================================================================
diff --git a/intern/cycles/kernel/kernel_light.h b/intern/cycles/kernel/kernel_light.h
index e7f62f2..b18f67a 100644
--- a/intern/cycles/kernel/kernel_light.h
+++ b/intern/cycles/kernel/kernel_light.h
@@ -167,12 +167,137 @@ ccl_device float3 sphere_light_sample(float3 P, float3 center, float radius, flo
return disk_light_sample(normalize(P - center), randu, randv)*radius;
}
-ccl_device float3 area_light_sample(float3 axisu, float3 axisv, float randu, float randv)
+/* Uses the following paper:
+ *
+ * Carlos Urena et al.
+ * An Area-Preserving Parametrization for Spherical Rectangles.
+ *
+ * https://www.solidangle.com/research/egsr2013_spherical_rectangle.pdf
+ */
+ccl_device float3 area_light_sample(float3 P,
+ float3 light_p,
+ float3 axisu, float3 axisv,
+ float randu, float randv,
+ float *pdf)
{
- randu = randu - 0.5f;
- randv = randv - 0.5f;
+ /* In our name system we're using P for the center,
+ * which is o in the paper.
+ */
+
+ float3 corner = light_p - axisu * 0.5f - axisv * 0.5f;
+ float axisu_len, axisv_len;
+ /* Compute local reference system R. */
+ float3 x = normalize_len(axisu, &axisu_len);
+ float3 y = normalize_len(axisv, &axisv_len);
+ float3 z = cross(x, y);
+ /* Compute rectangle coords in local reference system. */
+ float3 dir = corner - P;
+ float z0 = dot(dir, z);
+ /* Flip 'z' to make it point against Q. */
+ if(z0 > 0.0f) {
+ z *= -1.0f;
+ z0 *= -1.0f;
+ }
+ float z0sq = z0 * z0;
+ float x0 = dot(dir, x);
+ float y0 = dot(dir, y);
+ float x1 = x0 + axisu_len;
+ float y1 = y0 + axisv_len;
+ float y0sq = y0 * y0;
+ float y1sq = y1 * y1;
+ /* Create vectors to four vertices. */
+ float3 v00 = make_float3(x0, y0, z0);
+ float3 v01 = make_float3(x0, y1, z0);
+ float3 v10 = make_float3(x1, y0, z0);
+ float3 v11 = make_float3(x1, y1, z0);
+ /* Compute normals to edges. */
+ float3 n0 = normalize(cross(v00, v10));
+ float3 n1 = normalize(cross(v10, v11));
+ float3 n2 = normalize(cross(v11, v01));
+ float3 n3 = normalize(cross(v01, v00));
+ /* Compute internal angles (gamma_i). */
+ float g0 = acosf(-dot(n0, n1));
+ float g1 = acosf(-dot(n1, n2));
+ float g2 = acosf(-dot(n2, n3));
+ float g3 = acosf(-dot(n3, n0));
+ /* Compute predefined constants. */
+ float b0 = n0.z;
+ float b1 = n2.z;
+ float b0sq = b0 * b0;
+ float k = M_2PI_F - g2 - g3;
+ /* Compute solid angle from internal angles. */
+ float S = g0 + g1 - k;
+
+ /* Compute cu. */
+ float au = randu * S + k;
+ float fu = (cosf(au) * b0 - b1) / sinf(au);
+ float cu = 1.0f / sqrtf(fu * fu + b0sq) * (fu > 0.0f ? 1.0f : -1.0f);
+ cu = clamp(cu, -1.0f, 1.0f);
+ /* Compute xu. */
+ float xu = -(cu * z0) / sqrtf(1.0f - cu * cu);
+ xu = clamp(xu, x0, x1);
+ /* Compute yv. */
+ float d = sqrtf(xu * xu + z0sq);
+ float h0 = y0 / sqrtf(d * d + y0sq);
+ float h1 = y1 / sqrtf(d * d + y1sq);
+ float hv = h0 + randv * (h1 - h0), hv2 = hv * hv;
+ float yv = (hv2 < 1.0f - 1e-6f) ? (hv * d) / sqrtf(1.0f - hv2) : y1;
+
+ *pdf = 1.0f / S;
+
+ /* Transform (xu, yv, z0) to world coords. */
+ return P + xu * x + yv * y + z0 * z;
+}
- return axisu*randu + axisv*randv;
+/* TODO(sergey): This is actually a duplicated code from above, but how to avoid
+ * this without having some nasty function with loads of parameters?
+ */
+ccl_device float area_light_pdf(float3 P,
+ float3 light_p,
+ float3 axisu, float3 axisv)
+{
+ /* In our name system we're using P for the center,
+ * which is o in the paper.
+ */
+
+ float3 corner = light_p - axisu * 0.5f - axisv * 0.5f;
+ float axisu_len, axisv_len;
+ /* Compute local reference system R. */
+ float3 x = normalize_len(axisu, &axisu_len);
+ float3 y = normalize_len(axisv, &axisv_len);
+ float3 z = cross(x, y);
+ /* Compute rectangle coords in local reference system. */
+ float3 dir = corner - P;
+ float z0 = dot(dir, z);
+ /* Flip 'z' to make it point against Q. */
+ if(z0 > 0.0f) {
+ z *= -1.0f;
+ z0 *= -1.0f;
+ }
+ float x0 = dot(dir, x);
+ float y0 = dot(dir, y);
+ float x1 = x0 + axisu_len;
+ float y1 = y0 + axisv_len;
+ /* Create vectors to four vertices. */
+ float3 v00 = make_float3(x0, y0, z0);
+ float3 v01 = make_float3(x0, y1, z0);
+ float3 v10 = make_float3(x1, y0, z0);
+ float3 v11 = make_float3(x1, y1, z0);
+ /* Compute normals to edges. */
+ float3 n0 = normalize(cross(v00, v10));
+ float3 n1 = normalize(cross(v10, v11));
+ float3 n2 = normalize(cross(v11, v01));
+ float3 n3 = normalize(cross(v01, v00));
+ /* Compute internal angles (gamma_i). */
+ float g0 = acosf(-dot(n0, n1));
+ float g1 = acosf(-dot(n1, n2));
+ float g2 = acosf(-dot(n2, n3));
+ float g3 = acosf(-dot(n3, n0));
+ /* Compute predefined constants. */
+ float k = M_2PI_F - g2 - g3;
+ /* Compute solid angle from internal angles. */
+ float S = g0 + g1 - k;
+ return 1.0f / S;
}
ccl_device float spot_light_attenuation(float4 data1, float4 data2, LightSample *ls)
@@ -276,6 +401,7 @@ ccl_device void lamp_light_sample(KernelGlobals *kg, int lamp,
float4 data2 = kernel_tex_fetch(__light_data, lamp*LIGHT_SIZE + 2);
ls->eval_fac *= spot_light_attenuation(data1, data2, ls);
}
+ ls->pdf *= lamp_light_pdf(kg, ls->Ng, -ls->D, ls->t);
}
else {
/* area light */
@@ -286,18 +412,22 @@ ccl_device void lamp_light_sample(KernelGlobals *kg, int lamp,
float3 axisv = make_float3(data2.y, data2.z, data2.w);
float3 D = make_float3(data3.y, data3.z, data3.w);
- ls->P += area_light_sample(axisu, axisv, randu, randv);
+ ls->P = area_light_sample(P, ls->P,
+ axisu, axisv,
+ randu, randv,
+ &ls->pdf);
+
ls->Ng = D;
ls->D = normalize_len(ls->P - P, &ls->t);
float invarea = data2.x;
-
ls->eval_fac = 0.25f*invarea;
- ls->pdf = invarea;
+
+ if(dot(ls->D, D) > 0.0f)
+ ls->pdf = 0.0f;
}
ls->eval_fac *= kernel_data.integrator.inv_pdf_lights;
- ls->pdf *= lamp_light_pdf(kg, ls->Ng, -ls->D, ls->t);
}
}
@@ -355,8 +485,12 @@ ccl_device bool lamp_light_eval(KernelGlobals *kg, int lamp, float3 P, float3 D,
ls->D = D;
ls->t = FLT_MAX;
+ /* compute pdf */
float invarea = data1.w;
ls->pdf = invarea/(costheta*costheta*costheta);
+ if(ls->t != FLT_MAX)
+ ls->pdf *= lamp_light_pdf(kg, ls->Ng, -ls->D, ls->t);
+
ls->eval_fac = ls->pdf;
}
else if(type == LIGHT_POINT || type == LIGHT_SPOT) {
@@ -386,6 +520,10 @@ ccl_device bool lamp_light_eval(KernelGlobals *kg, int lamp, float3 P, float3 D,
if(ls->eval_fac == 0.0f)
return false;
}
+
+ /* compute pdf */
+ if(ls->t != FLT_MAX)
+ ls->pdf *= lamp_light_pdf(kg, ls->Ng, -ls->D, ls->t);
}
else if(type == LIGHT_AREA) {
/* area light */
@@ -412,16 +550,12 @@ ccl_device bool lamp_light_eval(KernelGlobals *kg, int lamp, float3 P, float3 D,
ls->D = D;
ls->Ng = Ng;
- ls->pdf = invarea;
- ls->eval_fac = 0.25f*ls->pdf;
+ ls->pdf = area_light_pdf(P, ls->P, axisu, axisv);
+ ls->eval_fac = 0.25f*invarea;
}
else
return false;
- /* compute pdf */
- if(ls->t != FLT_MAX)
- ls->pdf *= lamp_light_pdf(kg, ls->Ng, -ls->D, ls->t);
-
return true;
}
More information about the Bf-blender-cvs
mailing list