Corrections for the book Ray Tracing Gems II. The pages listed are for the released book, not for any preprints or other forms of the articles. A corrected copy of the free PDF version of the book can be found linked from http://raytracinggems.com as errors are discovered and fixed.
If you find an error, please let us know by emailing [email protected]
Page 49: Listing 3-2, the value computed for aspectScale should be divided by 2. This listing is also is missing pixel += vec2(0.5f) - (imageSize / 2.0f); after computing aspectScale.
The correct GLSL shader code for Listing 3-2 is:
// Pixel is the integer position >= 0 and < imageSize.
Ray generatePinholeRay(vec2 pixel)
{
float tanHalfAngle = tan(cameraFovAngle / 2.f);
float aspectScale = ((cameraFovDirection == 0) ? imageSize.x : imageSize.y) / 2.f;
pixel += vec2(0.5f) - (imageSize / 2.f);
vec3 direction = normalize(vec3(vec2(pixel.x, -pixel.y) * tanHalfAngle / aspectScale, -1));
return Ray(vec3(0.f), direction, 0.f, INFINITY);
}Page 54: Listing 3-6, the variable hvPan is used but not declared or defined. The variable distance should be defined as normalize(x, -y, -z);.
The correct GLSL shader code for Listing 3-6 is:
Ray paniniRay(vec2 pixel)
{
vec2 pixelCenterCoords = vec2(pixel) + vec2(0.5f) - (imageSize / 2.f);
float halfFOV = cameraFovAngle / 2.f;
float halfPaniniFOV = atan(sin(halfFOV), cos(halfFOV) + paniniDistance);
vec2 hvPan = vec2(tan(halfPaniniFOV)) * (1.f + paniniDistance);
hvPan *= pixelCenterCoords / (bool(cameraFovOrientation == 0) ? imageSize.x : imageSize.y);
hvPan.x = atan(hvPan.x / (1.0 + paniniDistance));
float M = sqrt(1 - square(sin(hvPan.x) * paniniDistance)) + paniniDistance * cos(hvPan.x);
float x = sin(hvPan.x) * M;
float z = (cos(hvPan.x) * M) - paniniDistance;
float S = (paniniDistance + 1) / (paniniDistance + z);
float y = lerp(hvPan.y / S, hvPan.y * z, verticalCompression);
vec3 direction = normalize(x, -y, -z);
return Ray(vec3(0.f), 0.f, direction, INFINITY);
}Page 55: Listing 3-7, lines 6, 8, and 10 are incorrect.
The correct GLSL shader code for Listing 3-7 is:
Ray generateFisheyeRay(vec2 pixel)
{
vec2 clampedHalfFOV = min(cameraFovAngle, pi) / 2.f;
vec2 angle = (pixel - imageSize / 2.f) * clampedHalfFOV;
if (cameraFovOrientation == 0) {
angle /= imageSize.x / 2.f;
} else if (cameraFovOrientation == 1) {
angle /= imageSize.y / 2.f;
} else {
angle /= length(imageSize) / 2.f;
}
// Don't generate rays for pixels outside the fisheye
// (circle and cropped circle only).
if (length(angle) > 0.5.f * pi) {
return Ray(vec3(0.f), 0.0f, vec3(0.f), -1);
}
vec3 dir = normalize(vec3(sin(angle.x), -sin(angle.y) * cos(angle.x), -cos(angle.x) * cos(angle.y)));
return Ray(vec3(0.f), 0.f, dir, INFINITY);
}Note: all scalars in this chapter can be coalesced into a single scalar, which multiplies two float2. After the below corrections, the code contains 15 scalar multiplications, but this can be reduced to 5. The corrected code removes the optimizations for clarity.
Page 81: Section 5.2.3, the BaryCentricWorldDerivatives() code listing near the bottom of the page has a few errors.
The correct code listing is:
void BarycentricWorldDerivatives(float3 A1, float3 A2, out float3 du_dx, out float3 dv_dx)
{
float3 Nt = cross(A1, A2);
du_dx = cross(A2, Nt) / dot(Nt, Nt);
dv_dx = cross(Nt, A1) / dot(Nt, Nt);
}Page 82: Section 5.2.4, the WorldScreenDerivatives() code listing in the middle of the page has an error related to the wMx variable.
The correct code listing is:
float3x3 WorldScreenDerivatives(float4x4 WorldToTargetMatrix, float4x4 TargetToWorldMatrix, float4 x)
{
float wMx = dot(WorldToTargetMatrix[3], x);
float3x3 dx_dxt = (float3x3)TargetToWorldMatrix;
dx_dxt[0] = wMx * (dx_dxt[0] - x.x * TargetToWorldMatrix[3].xyz);
dx_dxt[1] = wMx * (dx_dxt[1] - x.y * TargetToWorldMatrix[3].xyz);
dx_dxt[2] = wMx * (dx_dxt[2] - x.z * TargetToWorldMatrix[3].xyz);
return dx_dxt;
}Page 83: Section 5.2.6, the BarycentricDerivatives() code listing is updated based on the wMx variable changes in WorldScreenDerivatives().
The correct code listing is:
float2x2 BarycentricDerivatives(float4 x, float3 n, float3 x0, float3 x1, float3 x2,
float4x4 WorldToTargetMatrix , float4x4 TargetToWorldMatrix)
{
// Derivatives of barycentric coordinates with respect to
// world-space coordinates (Section 5.2.3).
float3 du_dx , dv_dx;
BarycentricWorldDerivatives(x1 - x0, x2 - x0, du_dx , dv_dx);
// Partial derivatives of world-space coordinates with respect
// to screen-space coordinates (Section 5.2.4). (Only the
// relevant 3x3 part is considered.)
float3x3 dx_dxt = WorldScreenDerivatives(WorldToTargetMatrix, TargetToWorldMatrix, x);
// Partial derivatives of barycentric coordinates with respect
// to screen-space coordinates.
float3 du_dxt = du_dx.x * dx_dxt[0] + du_dx.y * dx_dxt[1] + du_dx.z * dx_dxt[2];
float3 dv_dxt = dv_dx.x * dx_dxt[0] + dv_dx.y * dx_dxt[1] + dv_dx.z * dx_dxt[2];
// Derivatives of barycentric coordinates with respect to
// screen-space x and y coordinates (Section 5.2.5).
float2 ddepth_dXY = DepthGradient(x, n, TargetToWorldMatrix);
float2 du_dXY = du_dxt.xy + du_dxt.z * ddepth_dXY;
float2 dv_dXY = dv_dxt.xy + dv_dxt.z * ddepth_dXY;
return float2x2(du_dXY , dv_dXY);
}Page 118: Figure 10-4, the angle that is denoted α should instead be α/2
Page 119: Under equation 10-1, the 2nd sentence of the paragraph says we rotate by "+α" and "-α". It should read "+α/2" and "-α/2".
Page 260: line 17 of the code listing is incorrect. The HitGroupRecord structure's Padding1 variable should be removed since it is not necessary and its inclusion causes the structure size to not be a multiple of 32 bytes as required.
The correct code for the HitGroupRecord structure is:
struct HitGroupRecord
{
ShaderIdentifier ID;
D3D12_GPU_DESCRIPTOR_HANDLE SRVTableA = { };
D3D12_GPU_DESCRIPTOR_HANDLE SRVTableB = { };
uint64_t CBV = 0;
uint8_t Padding [8] = { }; // Needed to keep shader ID at 32-byte alignment
};None so far!
Thanks to Zander Majercik, @hatookov, Jeremy Ong, Leon Brands, and Tomas Akenine-Möller for reporting these errors.
Page last updated September 20, 2021