subd_patch.cpp

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/*
 * Copyright 2011-2013 Blender Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
 
/* Parts adapted from code in the public domain in NVidia Mesh Tools. */
 
#include "render/mesh.h"
 
#include "subd/subd_patch.h"
 
#include "util/util_math.h"
#include "util/util_types.h"
 
CCL_NAMESPACE_BEGIN
 
/* De Casteljau Evaluation */
 
static void decasteljau_cubic(float3 *P, float3 *dt, float t, const float3 cp[4])
{
  float3 d0 = cp[0] + t * (cp[1] - cp[0]);
  float3 d1 = cp[1] + t * (cp[2] - cp[1]);
  float3 d2 = cp[2] + t * (cp[3] - cp[2]);
 
  d0 += t * (d1 - d0);
  d1 += t * (d2 - d1);
 
  *P = d0 + t * (d1 - d0);
  if (dt)
    *dt = d1 - d0;
}
 
static void decasteljau_bicubic(
    float3 *P, float3 *du, float3 *dv, const float3 cp[16], float u, float v)
{
  float3 ucp[4], utn[4];
 
  /* interpolate over u */
  decasteljau_cubic(ucp + 0, utn + 0, u, cp);
  decasteljau_cubic(ucp + 1, utn + 1, u, cp + 4);
  decasteljau_cubic(ucp + 2, utn + 2, u, cp + 8);
  decasteljau_cubic(ucp + 3, utn + 3, u, cp + 12);
 
  /* interpolate over v */
  decasteljau_cubic(P, dv, v, ucp);
  if (du)
    decasteljau_cubic(du, NULL, v, utn);
}
 
/* Linear Quad Patch */
 
void LinearQuadPatch::eval(float3 *P, float3 *dPdu, float3 *dPdv, float3 *N, float u, float v)
{
  float3 d0 = interp(hull[0], hull[1], u);
  float3 d1 = interp(hull[2], hull[3], u);
 
  *P = interp(d0, d1, v);
 
  if (dPdu && dPdv) {
    *dPdu = interp(hull[1] - hull[0], hull[3] - hull[2], v);
    *dPdv = interp(hull[2] - hull[0], hull[3] - hull[1], u);
  }
 
  if (N) {
    *N = normalize(
        interp(interp(normals[0], normals[1], u), interp(normals[2], normals[3], u), v));
  }
}
 
BoundBox LinearQuadPatch::bound()
{
  BoundBox bbox = BoundBox::empty;
 
  for (int i = 0; i < 4; i++)
    bbox.grow(hull[i]);
 
  return bbox;
}
 
/* Bicubic Patch */
 
void BicubicPatch::eval(float3 *P, float3 *dPdu, float3 *dPdv, float3 *N, float u, float v)
{
  if (N) {
    float3 dPdu_, dPdv_;
    decasteljau_bicubic(P, &dPdu_, &dPdv_, hull, u, v);
 
    if (dPdu && dPdv) {
      *dPdu = dPdu_;
      *dPdv = dPdv_;
    }
 
    *N = normalize(cross(dPdu_, dPdv_));
  }
  else {
    decasteljau_bicubic(P, dPdu, dPdv, hull, u, v);
  }
}
 
BoundBox BicubicPatch::bound()
{
  BoundBox bbox = BoundBox::empty;
 
  for (int i = 0; i < 16; i++)
    bbox.grow(hull[i]);
 
  return bbox;
}
 
CCL_NAMESPACE_END