Tutorial going from 01_foundation to 02_basic, Step 6.2: Update Scene Buffer for Ray Tracing

[hlavacs]

This step is a bit confusing. It says to make sure that the following lines are there:

NVVK_DBG_SCOPE(cmd);  // <-- Helps to debug in NSight
const glm::mat4& viewMatrix = g_cameraManip->getViewMatrix();
const glm::mat4& projMatrix = g_cameraManip->getPerspectiveMatrix();

m_sceneResource.sceneInfo.viewProjMatrix = projMatrix * viewMatrix;   // Combine the view and projection matrices
m_sceneResource.sceneInfo.projInvMatrix  = glm::inverse(projMatrix);  // Inverse projection matrix
m_sceneResource.sceneInfo.viewInvMatrix  = glm::inverse(viewMatrix);  // Inverse view matrix
m_sceneResource.sceneInfo.cameraPosition = g_cameraManip->getEye();   // Get the camera position
m_sceneResource.sceneInfo.instances = (shaderio::GltfInstance*)m_sceneResource.bInstances.address;  // Get the address of the instance buffer

// ... rest of the function

However the function already contains

NVVK_DBG_SCOPE(cmd);  // <-- Helps to debug in NSight
const glm::mat4& viewMatrix = m_cameraManip->getViewMatrix();
const glm::mat4& projMatrix = m_cameraManip->getPerspectiveMatrix();

m_sceneResource.sceneInfo.viewProjMatrix = projMatrix * viewMatrix;  // Combine the view and projection matrices
m_sceneResource.sceneInfo.cameraPosition = m_cameraManip->getEye();  // Get the camera position
m_sceneResource.sceneInfo.instances = (shaderio::GltfInstance*)m_sceneResource.bInstances.address;  // Get the address of the instance buffer
m_sceneResource.sceneInfo.meshes = (shaderio::GltfMesh*)m_sceneResource.bMeshes.address;  // Get the address of the mesh buffer
m_sceneResource.sceneInfo.materials = (shaderio::GltfMetallicRoughness*)m_sceneResource.bMaterials.address;  // Get the address of the material buffer

Better to explicitly declare the lines to add:

m_sceneResource.sceneInfo.projInvMatrix  = glm::inverse(projMatrix);  // Inverse projection matrix
m_sceneResource.sceneInfo.viewInvMatrix  = glm::inverse(viewMatrix);  // Inverse view matrix

[mklefrancois]

Thanks for pointing this out, and for the suggestion.

I will change this for the following, which hopefully would make clearer.

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Find the updateSceneBuffer() method and add the two inverse matrix lines as shown below:

m_sceneResource.sceneInfo.viewProjMatrix = projMatrix * viewMatrix;   // Combine the view and projection matrices
m_sceneResource.sceneInfo.projInvMatrix  = glm::inverse(projMatrix);  // Inverse projection matrix (NEW)
m_sceneResource.sceneInfo.viewInvMatrix  = glm::inverse(viewMatrix);  // Inverse view matrix (NEW)
m_sceneResource.sceneInfo.cameraPosition = m_cameraManip->getEye();   // Get the camera position