diff options
Diffstat (limited to 'extern/draco/draco/src/draco/compression/attributes/normal_compression_utils.h')
| -rw-r--r-- | extern/draco/draco/src/draco/compression/attributes/normal_compression_utils.h | 133 |
1 files changed, 75 insertions, 58 deletions
diff --git a/extern/draco/draco/src/draco/compression/attributes/normal_compression_utils.h b/extern/draco/draco/src/draco/compression/attributes/normal_compression_utils.h index 32e27c711e3..be5ee5b09e3 100644 --- a/extern/draco/draco/src/draco/compression/attributes/normal_compression_utils.h +++ b/extern/draco/draco/src/draco/compression/attributes/normal_compression_utils.h @@ -53,6 +53,7 @@ class OctahedronToolBox { : quantization_bits_(-1), max_quantized_value_(-1), max_value_(-1), + dequantization_scale_(1.f), center_value_(-1) {} bool SetQuantizationBits(int32_t q) { @@ -62,6 +63,7 @@ class OctahedronToolBox { quantization_bits_ = q; max_quantized_value_ = (1 << quantization_bits_) - 1; max_value_ = max_quantized_value_ - 1; + dequantization_scale_ = 2.f / max_value_; center_value_ = max_value_ / 2; return true; } @@ -192,64 +194,11 @@ class OctahedronToolBox { } } - // TODO(b/149328891): Change function to not use templates as |T| is only - // float. - template <typename T> - void OctaherdalCoordsToUnitVector(T in_s, T in_t, T *out_vector) const { - DRACO_DCHECK_GE(in_s, 0); - DRACO_DCHECK_GE(in_t, 0); - DRACO_DCHECK_LE(in_s, 1); - DRACO_DCHECK_LE(in_t, 1); - T s = in_s; - T t = in_t; - T spt = s + t; - T smt = s - t; - T x_sign = 1.0; - if (spt >= 0.5 && spt <= 1.5 && smt >= -0.5 && smt <= 0.5) { - // Right hemisphere. Don't do anything. - } else { - // Left hemisphere. - x_sign = -1.0; - if (spt <= 0.5) { - s = 0.5 - in_t; - t = 0.5 - in_s; - } else if (spt >= 1.5) { - s = 1.5 - in_t; - t = 1.5 - in_s; - } else if (smt <= -0.5) { - s = in_t - 0.5; - t = in_s + 0.5; - } else { - s = in_t + 0.5; - t = in_s - 0.5; - } - spt = s + t; - smt = s - t; - } - const T y = 2.0 * s - 1.0; - const T z = 2.0 * t - 1.0; - const T x = std::min(std::min(2.0 * spt - 1.0, 3.0 - 2.0 * spt), - std::min(2.0 * smt + 1.0, 1.0 - 2.0 * smt)) * - x_sign; - // Normalize the computed vector. - const T normSquared = x * x + y * y + z * z; - if (normSquared < 1e-6) { - out_vector[0] = 0; - out_vector[1] = 0; - out_vector[2] = 0; - } else { - const T d = 1.0 / std::sqrt(normSquared); - out_vector[0] = x * d; - out_vector[1] = y * d; - out_vector[2] = z * d; - } - } - - template <typename T> - void QuantizedOctaherdalCoordsToUnitVector(int32_t in_s, int32_t in_t, - T *out_vector) const { - T scale = 1.0 / static_cast<T>(max_value_); - OctaherdalCoordsToUnitVector(in_s * scale, in_t * scale, out_vector); + inline void QuantizedOctahedralCoordsToUnitVector(int32_t in_s, int32_t in_t, + float *out_vector) const { + OctahedralCoordsToUnitVector(in_s * dequantization_scale_ - 1.f, + in_t * dequantization_scale_ - 1.f, + out_vector); } // |s| and |t| are expected to be signed values. @@ -333,9 +282,77 @@ class OctahedronToolBox { int32_t center_value() const { return center_value_; } private: + inline void OctahedralCoordsToUnitVector(float in_s_scaled, float in_t_scaled, + float *out_vector) const { + // Background about the encoding: + // A normal is encoded in a normalized space <s, t> depicted below. The + // encoding correponds to an octahedron that is unwrapped to a 2D plane. + // During encoding, a normal is projected to the surface of the octahedron + // and the projection is then unwrapped to the 2D plane. Decoding is the + // reverse of this process. + // All points in the central diamond are located on triangles on the + // right "hemisphere" of the octahedron while all points outside of the + // diamond are on the left hemisphere (basically, they would have to be + // wrapped along the diagonal edges to form the octahedron). The central + // point corresponds to the right most vertex of the octahedron and all + // corners of the plane correspond to the left most vertex of the + // octahedron. + // + // t + // ^ *-----*-----* + // | | /|\ | + // | / | \ | + // | / | \ | + // | / | \ | + // *-----*---- * + // | \ | / | + // | \ | / | + // | \ | / | + // | \|/ | + // *-----*-----* --> s + + // Note that the input |in_s_scaled| and |in_t_scaled| are already scaled to + // <-1, 1> range. This way, the central point is at coordinate (0, 0). + float y = in_s_scaled; + float z = in_t_scaled; + + // Remaining coordinate can be computed by projecting the (y, z) values onto + // the surface of the octahedron. + const float x = 1.f - std::abs(y) - std::abs(z); + + // |x| is essentially a signed distance from the diagonal edges of the + // diamond shown on the figure above. It is positive for all points in the + // diamond (right hemisphere) and negative for all points outside the + // diamond (left hemisphere). For all points on the left hemisphere we need + // to update their (y, z) coordinates to account for the wrapping along + // the edges of the diamond. + float x_offset = -x; + x_offset = x_offset < 0 ? 0 : x_offset; + + // This will do nothing for the points on the right hemisphere but it will + // mirror the (y, z) location along the nearest diagonal edge of the + // diamond. + y += y < 0 ? x_offset : -x_offset; + z += z < 0 ? x_offset : -x_offset; + + // Normalize the computed vector. + const float norm_squared = x * x + y * y + z * z; + if (norm_squared < 1e-6) { + out_vector[0] = 0; + out_vector[1] = 0; + out_vector[2] = 0; + } else { + const float d = 1.0f / std::sqrt(norm_squared); + out_vector[0] = x * d; + out_vector[1] = y * d; + out_vector[2] = z * d; + } + } + int32_t quantization_bits_; int32_t max_quantized_value_; int32_t max_value_; + float dequantization_scale_; int32_t center_value_; }; } // namespace draco |