Method performPicking

samples/Picking3D/src/Picking3DApp.cpp:130–200

}

bool Picking3DApp::performPicking( vec3 *pickedPoint, vec3 *pickedNormal )
{
	// Generate a ray from the camera into our world. Note that we have to
	// flip the vertical coordinate.
	float u = mMousePos.x / (float) getWindowWidth();
	float v = mMousePos.y / (float) getWindowHeight();
	Ray ray = mCamera.generateRay( u, 1.0f - v, mCamera.getAspectRatio() );

	// The coordinates of the bounding box are in object space, not world space,
	// so if the model was translated, rotated or scaled, the bounding box would not
	// reflect that. One solution would be to pass the transformation to the calcBoundingBox() function:
	AxisAlignedBox worldBoundsExact = mTriMesh->calcBoundingBox( mTransform ); // slow

	// But if you already have an object space bounding box, it's much faster to
	// approximate the world space bounding box like this:
	AxisAlignedBox worldBoundsApprox = mObjectBounds.transformed( mTransform ); // fast

	// Draw the object space bounding box in yellow. It will not animate,
	// because animation is done in world space.
	drawCube( mObjectBounds, Color( 1, 1, 0 ) );

	// Draw the exact bounding box in orange.
	drawCube( worldBoundsExact, Color( 1, 0.5f, 0 ) );

	// Draw the approximated bounding box in cyan.
	drawCube( worldBoundsApprox, Color( 0, 1, 1 ) );

	// Perform fast detection first - test against the bounding box itself.
	if( ! worldBoundsExact.intersects( ray ) )
		return false;

	// Set initial distance to something far, far away.
	float result = FLT_MAX;

	// Traverse triangle list and find the closest intersecting triangle.
	const size_t polycount = mTriMesh->getNumTriangles();

	float distance = 0.0f;
	for( size_t i = 0; i < polycount; ++i ) {
		// Get a single triangle from the mesh.
		vec3 v0, v1, v2;
		mTriMesh->getTriangleVertices( i, &v0, &v1, &v2 );

		// Transform triangle to world space.
		v0 = vec3( mTransform * vec4( v0, 1.0 ) );
		v1 = vec3( mTransform * vec4( v1, 1.0 ) );
		v2 = vec3( mTransform * vec4( v2, 1.0 ) );

		// Test to see if the ray intersects this triangle.
		if( ray.calcTriangleIntersection( v0, v1, v2, &distance ) ) {
			// Keep the result if it's closer than any intersection we've had so far.
			if( distance < result ) {
				result = distance;

				// Assuming this is the closest triangle, we'll calculate our normal
				// while we've got all the points handy.
				*pickedNormal = normalize( cross( v1 - v0, v2 - v0 ) );
			}