message: update tfn api
diff: @@ -56,7 +56,6 @@ vec4f DRR_integrateVolumeInterval(
  vec3f color = make_vec3f(0.f);
  float alpha = 0.f;
  - float pSample = -1.f;
  foreach_unique (vm in volModel) {
  Volume *uniform volume = vm->volume;
  @@ -68,19 +67,14 @@ vec4f DRR_integrateVolumeInterval(
  const float sample = volume->sample(volume, ray.org + ray.t0 * ray.dir);
  if (!isnan(sample)) {
  - vec3f sampleColor = tf->getIntegratedColorForValue(tf, pSample, sample);
  - float sampleAlpha =
  - tf->getIntegratedOpacityForValue(tf, pSample, sample);
  + vec4f sampleColorOpacity = tf->get(tf, sample);
  - pSample = sample;
  + const float clampedOpacity =
  + clamp(sampleColorOpacity.w / vm->samplingRate);
  - const float clampedOpacity = clamp(sampleAlpha / vm->samplingRate);
  -
  - sampleColor = sampleColor * clampedOpacity;
  - sampleAlpha = clampedOpacity;
  -
  - color = color + ((1.f - alpha) * sampleColor);
  - alpha = alpha + ((1.f - alpha) * sampleAlpha);
  + color = color
  + + ((1.f - alpha) * clampedOpacity * make_vec3f(sampleColorOpacity));
  + alpha = alpha + ((1.f - alpha) * clampedOpacity);
  }
  volume->stepRay(volume, tf, ray, vm->samplingRate);
  