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Replace the ray tracer with a more precise and complete one
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Bounding boxes that are smaller than the node (e.g. flowers) are handled. In future it shouldn't be hard to add handling of multiple selection boxes per node.

Fixes #33.
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Pedro Gimeno committed Feb 16, 2020
1 parent c4ea0d8 commit b0d2998
Showing 1 changed file with 162 additions and 44 deletions.
206 changes: 162 additions & 44 deletions client/source/hud/BlockCursor.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -252,20 +252,150 @@ float BlockCursor::fract(float value) const {
else return f;
}

enum Axis {
AXIS_X,
AXIS_Y,
AXIS_Z
};

static inline glm::dvec3 intersectAxisPlane(const Axis axis, const double coord,
const glm::dvec3 &position,
const glm::dvec3 &direction) {
glm::dvec3 result;
const double t = axis == AXIS_X ? (coord - position.x) / direction.x
: axis == AXIS_Y ? (coord - position.y) / direction.y
: (coord - position.z) / direction.z;
result.x = axis == AXIS_X ? coord : position.x + t * direction.x;
result.y = axis == AXIS_Y ? coord : position.y + t * direction.y;
result.z = axis == AXIS_Z ? coord : position.z + t * direction.z;
return result;
}

static inline void recordHit(const glm::dvec3 &position,
const glm::dvec3 &isect,
const Axis axis,
const bool neg,
const int_fast32_t nx,
const int_fast32_t ny,
const int_fast32_t nz,
int_fast32_t &bestX,
int_fast32_t &bestY,
int_fast32_t &bestZ,
int_fast8_t &bestFace,
double &bestDepth,
bool &hit) {
// Check if we have a record
double depth = glm::distance(position, isect);
if (bestFace == -1 || depth < bestDepth) {
// Yep, register it
bestFace = axis == AXIS_X ? (neg ? 0 : 3)
: axis == AXIS_Y ? (neg ? 1 : 4)
: (neg ? 2 : 5);
bestDepth = depth;
bestX = nx;
bestY = ny;
bestZ = nz;
}
hit = true;
}

static inline void rayCastToAxis(const Axis axis, const glm::dvec3 &position,
const glm::dvec3 &lookAt,
const double maxReach,
int_fast32_t &bestX, int_fast32_t &bestY,
int_fast32_t &bestZ,
int_fast8_t &bestFace, double &bestDepth,
const ClientWorld &world) {
int_fast8_t dir;
int_fast32_t firstNodeRow, lastNodeRow;
glm::dvec3 isect;
double posCoord, lookAtCoord;

// The line that starts at 'position' and goes in the direction
// of 'lookAt' with length 'maxReach' crosses several nodes in
// the X direction at integer positions. Determine the first and
// last such positions.
switch(axis) {
case AXIS_X:
posCoord = position.x;
lookAtCoord = lookAt.x;
break;
case AXIS_Y:
posCoord = position.y;
lookAtCoord = lookAt.y;
break;
default:
posCoord = position.z;
lookAtCoord = lookAt.z;
break;
}
firstNodeRow = int_fast32_t(floor(posCoord));
lastNodeRow = int_fast32_t(floor(posCoord + lookAtCoord * maxReach));

dir = (lookAtCoord > 0.) - (lookAtCoord < 0.);
if (!dir) {
// Can't cross any planes if it doesn't change in this axis
return;
}

for(int_fast32_t nodeRow = firstNodeRow + dir;
dir > 0 ? (nodeRow <= lastNodeRow) : (nodeRow >= lastNodeRow); nodeRow += dir) {
int_fast32_t nx, ny, nz;

isect = intersectAxisPlane(axis, double(nodeRow + (dir < 0)), position, lookAt);

nx = axis == AXIS_X ? nodeRow : floor(isect.x);
ny = axis == AXIS_Y ? nodeRow : floor(isect.y);
nz = axis == AXIS_Z ? nodeRow : floor(isect.z);
u32 blockID = world.getBlock(nx, ny, nz);

const Block &block = Registry::getInstance().getBlock(blockID);
if(blockID && block.drawType() != BlockDrawType::Liquid) {
// Check bounding box; this should loop over all selection boxes
// when they are implemented
gk::FloatBox selBox = block.boundingBox();
selBox.x += double(nx);
selBox.y += double(ny);
selBox.z += double(nz);

bool hit = false;

// Check if we hit any of the sides of the inner box
isect = intersectAxisPlane(AXIS_X, (lookAt.x < 0. ? selBox.x + selBox.width : selBox.x), position, lookAt);
if (selBox.y <= isect.y && isect.y <= selBox.y + selBox.height
&& selBox.z <= isect.z && isect.z <= selBox.z + selBox.depth)
recordHit(position, isect, AXIS_X, lookAt.x < 0., nx, ny, nz, bestX, bestY, bestZ, bestFace, bestDepth, hit);

isect = intersectAxisPlane(AXIS_Y, (lookAt.y < 0. ? selBox.y + selBox.height : selBox.y), position, lookAt);
if (selBox.x <= isect.x && isect.x <= selBox.x + selBox.width
&& selBox.z <= isect.z && isect.z <= selBox.z + selBox.depth)
recordHit(position, isect, AXIS_Y, lookAt.y < 0., nx, ny, nz, bestX, bestY, bestZ, bestFace, bestDepth, hit);

isect = intersectAxisPlane(AXIS_Z, (lookAt.z < 0. ? selBox.z + selBox.depth : selBox.z), position, lookAt);
if (selBox.x <= isect.x && isect.x <= selBox.x + selBox.width
&& selBox.y <= isect.y && isect.y <= selBox.y + selBox.height)
recordHit(position, isect, AXIS_Z, lookAt.z < 0., nx, ny, nz, bestX, bestY, bestZ, bestFace, bestDepth, hit);

if (hit)
break; // no need to check deeper
}
}
}

glm::vec4 BlockCursor::findSelectedBlock(bool useDepthBuffer) const {
int mx, my, mz;
int face = -1;
int_fast32_t mx, my, mz;
int_fast32_t face = -1;

glm::vec3 lookAt{m_player.pointTargetedX() - m_player.camera().getPosition().x,
m_player.pointTargetedY() - m_player.camera().getPosition().y,
m_player.pointTargetedZ() - m_player.camera().getPosition().z};
glm::dvec3 lookAt{m_player.pointTargetedX() - m_player.camera().getPosition().x,
m_player.pointTargetedY() - m_player.camera().getPosition().y,
m_player.pointTargetedZ() - m_player.camera().getPosition().z};

glm::vec3 position{m_player.camera().getPosition().x,
m_player.camera().getPosition().y,
m_player.camera().getPosition().z};
glm::dvec3 position{m_player.camera().getPosition().x,
m_player.camera().getPosition().y,
m_player.camera().getPosition().z};

// FIXME: Add max distance
if(useDepthBuffer) {
// FIXME: Add max distance
// At which voxel are we looking? First, find out coords of the center pixel
float depth;
glCheck(glReadPixels(Config::screenWidth / 2.0f, Config::screenHeight / 2.0f, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &depth));
Expand Down Expand Up @@ -303,44 +433,32 @@ glm::vec4 BlockCursor::findSelectedBlock(bool useDepthBuffer) const {
if(face == 0 && lookAt.x > 0) face += 3;
if(face == 1 && lookAt.y > 0) face += 3;
if(face == 2 && lookAt.z > 0) face += 3;
} else {
// Very naive ray casting algorithm to find out which block we are looking at
glm::vec3 testPos = position;
glm::vec3 prevPos = position;

for(int i = 0 ; i < 100 ; i++) {
// Advance from our current position to the direction we are looking at, in small steps
prevPos = testPos;
testPos += lookAt * 0.1f;

mx = floorf(testPos.x);
my = floorf(testPos.y);
mz = floorf(testPos.z);

// If we find a block that is not air, we are done
u32 blockID = m_world.getBlock(mx, my, mz);
const Block &block = Registry::getInstance().getBlock(blockID);
if(blockID && block.drawType() != BlockDrawType::Liquid) break;

// If we are looking at air, disable the cursor
u32 blockID = m_world.getBlock(mx, my, mz);
const Block &block = Registry::getInstance().getBlock(blockID);
if(!blockID || block.drawType() == BlockDrawType::Liquid) {
face = -1;
}

// Find out which face of the block we are looking at
int px = floorf(prevPos.x);
int py = floorf(prevPos.y);
int pz = floorf(prevPos.z);

if(px > mx) face = 0;
else if(px < mx) face = 3;
else if(py > my) face = 1;
else if(py < my) face = 4;
else if(pz > mz) face = 2;
else if(pz < mz) face = 5;
}
} else {
// Ray casting algorithm to find out which block we are looking at

const double maxReach = 10.;
double bestDepth;
int_fast8_t bestFace = -1;
int_fast32_t bestX = 0, bestY = 0, bestZ = 0;

glm::dvec3 lookAtN = glm::normalize(lookAt);

rayCastToAxis(AXIS_X, position, lookAtN, maxReach, bestX, bestY, bestZ, bestFace, bestDepth, m_world);
rayCastToAxis(AXIS_Y, position, lookAtN, maxReach, bestX, bestY, bestZ, bestFace, bestDepth, m_world);
rayCastToAxis(AXIS_Z, position, lookAtN, maxReach, bestX, bestY, bestZ, bestFace, bestDepth, m_world);

// If we are looking at air, disable the cursor
u32 blockID = m_world.getBlock(mx, my, mz);
const Block &block = Registry::getInstance().getBlock(blockID);
if(!blockID || block.drawType() == BlockDrawType::Liquid) {
face = -1;
mx = bestX;
my = bestY;
mz = bestZ;
face = bestFace;
}

return {mx, my, mz, face};
Expand Down

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