[ChunkRenderer] Frustum culling implemented thanks to pgimeno's work.
See https://git.unarelith.net/Unarelith/OpenMiner/pulls/39
This commit is contained in:
Quentin Bazin
parent
26fbc8737c
commit
791e41ce36
@ -33,6 +33,33 @@
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#include "ChunkRenderer.hpp"
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#include "ClientChunk.hpp"
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inline static bool bbIntersects(const glm::vec3 &a0, const glm::vec3 &a1, const glm::vec3 &b0, const glm::vec3 &b1) {
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return (std::max(a0.x, b0.x) <= std::min(a1.x, b1.x))
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& (std::max(a0.y, b0.y) <= std::min(a1.y, b1.y))
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& (std::max(a0.z, b0.z) <= std::min(a1.z, b1.z));
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}
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inline static bool isOutside(const glm::vec3 &v, const glm::vec3 &n) {
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// Return whether a vertex is on the positive side of the plane given by
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// position (0, 0, 0) and normal n.
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return glm::dot(v, n) >= 0.f;
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}
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static bool fullyOutside(const glm::vec3 &v1, const glm::vec3 &v2, const glm::vec3 &n) {
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// A polyhedron is fully on one side of the axis iff all of its vertices
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// are. This function tests whether all 8 vertices of an axis-aligned box
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// given by the two corners v1, v2 are on the positive side of the plane
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// with normal n that goes through the origin.
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return isOutside(v1, n)
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&& isOutside(v2, n)
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&& isOutside(glm::vec3{v2.x, v1.y, v1.z}, n)
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&& isOutside(glm::vec3{v1.x, v2.y, v2.z}, n)
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&& isOutside(glm::vec3{v1.x, v2.y, v1.z}, n)
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&& isOutside(glm::vec3{v2.x, v1.y, v2.z}, n)
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&& isOutside(glm::vec3{v2.x, v2.y, v1.z}, n)
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&& isOutside(glm::vec3{v1.x, v1.y, v2.z}, n);
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}
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void ChunkRenderer::draw(gk::RenderTarget &target, gk::RenderStates states, const ChunkMap &chunks, gk::Camera &camera, const Sky *currentSky) const {
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// Changing the values sent to the GPU to double precision is suicidal,
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// performance wise, if possible at all. Therefore we want to keep the
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@ -50,67 +77,185 @@ void ChunkRenderer::draw(gk::RenderTarget &target, gk::RenderStates states, cons
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// vertex coordinates passed to the renderer are all small, and single
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// precision floats suffice for the drawing.
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gk::Vector3d cameraPos(camera.getDPosition());
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const gk::Vector3d cameraPos{camera.getDPosition()};
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camera.setDPosition(0, 0, 0); // Temporarily move the camera to the origin
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// Calculate the Z of the normalized device coordinate of the render distance plane
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float farZ;
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{
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glm::vec4 farVec{0.f, 0.f, -float(Config::renderDistance * CHUNK_WIDTH), 1.f};
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farVec = target.getView()->getTransform().getMatrix() * farVec;
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farZ = farVec.z / farVec.w;
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}
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// Pre-calculate product of Projection and View matrices
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const glm::mat4 pv = target.getView()->getTransform().getMatrix()
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* target.getView()->getViewTransform().getMatrix();
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glm::vec3 frustumVertex[8]; // Frustum vertices
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// Look-at vector (vector the camera is pointing to). It's the Z vector
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// of the inverse of the view matrix. Since the camera is at the origin,
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// the view matrix does not displace, therefore its inverse is the
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// transpose, possibly scaled. But we don't care if the lookat vector is
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// scaled for this purpose.
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const glm::vec3 lookAt{
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-target.getView()->getViewTransform().getMatrix()[0].z,
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-target.getView()->getViewTransform().getMatrix()[1].z,
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-target.getView()->getViewTransform().getMatrix()[2].z,
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};
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glm::vec3 fbb0, fbb1; // Corners of the frustum's AABB
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{
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// Inverse of the PV, used to find the frustum corners in world space
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const glm::mat4 ipv{glm::inverse(pv)};
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int i = 0;
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// Transform the corners of the NDC cube to camera coords.
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// That's where the frustum corners are. Note that we need the
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// frustum truncated by the render distance plane, so we do it here.
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for (float z = -1.f; z <= 1.f; z += 2.f)
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for (float y = -1.f; y <= 1.f; y += 2.f)
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for (float x = -1.f; x <= 1.f; x += 2.f) {
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// Truncate the frustum with the render distance
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glm::vec4 v{ipv * glm::vec4{x, y, std::min(z, farZ), 1.f}};
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v.x /= v.w;
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v.y /= v.w;
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v.z /= v.w;
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frustumVertex[i].x = v.x;
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frustumVertex[i].y = v.y;
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frustumVertex[i].z = v.z;
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++i;
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}
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// Find the axes-aligned bounding box of the frustum
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fbb0 = glm::vec3{frustumVertex[0]};
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fbb1 = glm::vec3{frustumVertex[0]};
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for (i = 1; i < 8; ++i) {
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// Bottom-left-front corner
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fbb0.x = std::min(fbb0.x, frustumVertex[i].x);
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fbb0.y = std::min(fbb0.y, frustumVertex[i].y);
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fbb0.z = std::min(fbb0.z, frustumVertex[i].z);
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// Top-right-back corner
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fbb1.x = std::max(fbb1.x, frustumVertex[i].x);
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fbb1.y = std::max(fbb1.y, frustumVertex[i].y);
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fbb1.z = std::max(fbb1.z, frustumVertex[i].z);
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}
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}
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// Prepare a list of chunks to draw
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std::vector<std::pair<ClientChunk*, gk::Transform>> chunksToDraw;
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for(auto &it : chunks) {
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if (!it.second->isInitialized()) continue;
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it.second->setHasBeenDrawn(false);
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gk::Transform tf = glm::translate(glm::mat4(1.0f),
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glm::vec3(it.second->x() * CHUNK_WIDTH - cameraPos.x,
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it.second->y() * CHUNK_DEPTH - cameraPos.y,
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it.second->z() * CHUNK_HEIGHT - cameraPos.z));
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// Is the chunk close enough?
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glm::vec4 center = target.getView()->getViewTransform().getMatrix()
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* tf.getMatrix()
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* glm::vec4(CHUNK_WIDTH / 2, CHUNK_DEPTH / 2, CHUNK_HEIGHT / 2, 1);
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// Nope, too far, don't render it
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if(glm::length(center) > (Config::renderDistance + 1.f) * CHUNK_WIDTH) {
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if(floor(glm::length(center)) > (Config::renderDistance + 2.f) * CHUNK_WIDTH) {
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it.second->setTooFar(true);
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if (!it.second->isInitialized())
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m_onChunkDeletionRequested(gk::Vector3i{it.second->x(), it.second->y(), it.second->z()});
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}
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continue;
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}
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it.second->setTooFar(false);
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if (!it.second->isInitialized()) continue;
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// Apply the Separating Axis Theorem to determine visibility of each
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// chunk. This theorem states that two convex figures don't intersect
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// if, and only if, there's an axis (a line in the case of 2D, a
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// plane in the case of 3D) such that one figure lies completely on
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// one side of the axis and the other lies completely on the other
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// side.
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//
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// Furthermore, if the figures are polygons (2D) or polyhedrons (3D),
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// one of the faces of one of them should be a separating axis, if
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// there's one. But this face can belong to either of the shapes, so
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// all faces of both shapes need to be checked until either one is
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// found which is a separating axis, or none is (in the latter case,
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// the shapes intersect).
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// Is this chunk's centre on the screen?
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float d = glm::length2(center);
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center.x /= center.w;
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center.y /= center.w;
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// The goal here is to check if the frustum intersects the chunk's
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// bounding box, which is an axes-aligned box, and we take advantage
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// of that, because checking all the points of a shape against an
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// axis-aligned box is equivalent to checking intersection between
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// both shapes' axis-aligned bounding boxes. Therefore, our first
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// check will apply the theorem to the sides of the chunk's bounding
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// box, against the frustum's AABB which we have calculated before.
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// This effectively checks if any of the sides of the chunk's BB is a
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// separating axis, in the sense of the theorem.
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// Find bottom-left-front corner of chunk's BB (in cameraPos coords)
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const glm::vec3 chunkBB0{
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it.second->x() * CHUNK_WIDTH - cameraPos.x,
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it.second->y() * CHUNK_DEPTH - cameraPos.y,
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it.second->z() * CHUNK_HEIGHT - cameraPos.z,
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};
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// Find top-right-back corner of chunk's BB
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const glm::vec3 chunkBB1{
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chunkBB0.x + CHUNK_WIDTH,
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chunkBB0.y + CHUNK_DEPTH,
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chunkBB0.z + CHUNK_HEIGHT
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};
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// Check if it's too far (temporary hack for removing chunks, until
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// it's performed with a timeout)
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const float dist = glm::length((chunkBB0 + chunkBB1) / 2.f);
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if (dist > glm::length(frustumVertex[4]) + glm::length(glm::vec3{CHUNK_WIDTH, CHUNK_DEPTH, CHUNK_HEIGHT}) / 2.f) {
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it.second->setTooFar(true);
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// If it is behind the camera, don't bother drawing it.
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// Our screen coordinates are +X right, +Y up, and for a right-handed
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// coordinate system, depth must be negative Z, so anything with a
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// positive Z is behind the camera.
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if (center.z > CHUNK_MAXSIZE) {
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continue;
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}
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// If it is outside the screen, don't bother drawing it
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if (fabsf(center.x) > 1 + fabsf(CHUNK_HEIGHT * 2 / center.w)
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|| fabsf(center.y) > 1 + fabsf(CHUNK_HEIGHT * 2 / center.w)) {
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// FIXME: Disable this test; one that considers all eight corners of the chunk is needed instead.
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//continue;
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}
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// Check if the frustum's BB intersects the chunk's BB.
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// This discards the big majority of chunks, and the more expensive
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// tests will be done only on a handful on them, of which roughly
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// one third will be visible.
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if (!bbIntersects(chunkBB0, chunkBB1, fbb0, fbb1))
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continue;
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// Now it's the turn to check each of the frustum's faces against the
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// chunk's BB. If none of them is a separating axis, then the frustum
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// and the chunk's BB definitively intersect, i.e. the BB is visible.
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// We'll consider the frustum as a pyramid, i.e. we'll ignore the
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// near clipping plane. This is OK because the worst case is that
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// we'll render up to 4 more chunks than necessary, in the rare
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// event that the corner of the chunks is within the tiny pyramid
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// situated between the near plane and the camera's position. This
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// saves one of the checks.
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// All frustum planes considered except one intersect the camera's
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// origin. For that one (see next check) we subtract the vertex from
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// the BB corners, to make the test correct.
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// The far plane (or more precisely, the render distance plane) uses
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// the lookat vector as the normal. Any vertex on the far side of the
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// clipped frustum will do as position. This check is also used to
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// set the TooFar flag on the chunk.
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if (fullyOutside(chunkBB0 - frustumVertex[4], chunkBB1 - frustumVertex[4], lookAt))
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continue;
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// Check the chunk's BB against the remaining 4 frustum planes.
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// Normals (cross products) must be calculated in right-hand order
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// so that all normals point outwards of the frustum (pyramid).
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// The top and bottom planes discard the most chunks, because the
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// frustum is narrower in the vertical direction, so they are checked
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// first.
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if (fullyOutside(chunkBB0, chunkBB1, glm::cross(frustumVertex[4], frustumVertex[5]))
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|| fullyOutside(chunkBB0, chunkBB1, glm::cross(frustumVertex[7], frustumVertex[6]))
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|| fullyOutside(chunkBB0, chunkBB1, glm::cross(frustumVertex[5], frustumVertex[7]))
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|| fullyOutside(chunkBB0, chunkBB1, glm::cross(frustumVertex[6], frustumVertex[4]))
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)
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continue;
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// If this chunk is not initialized, skip it and request meshing
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if(!it.second->isReadyForMeshing()) {
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m_onMeshingRequested(d, gk::Vector3i{it.second->x(), it.second->y(), it.second->z()});
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m_onMeshingRequested(dist, gk::Vector3i{it.second->x(), it.second->y(), it.second->z()});
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continue;
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}
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// The chunk's model matrix is a pure translation matrix whose origin
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// is the chunk's origin in cameraPos coordinates.
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const glm::mat4 tf{1.f, 0.f, 0.f, 0.f,
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0.f, 1.f, 0.f, 0.f,
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0.f, 0.f, 1.f, 0.f,
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chunkBB0.x, chunkBB0.y, chunkBB0.z, 1.f};
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chunksToDraw.emplace_back(it.second.get(), tf);
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}
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