A technique for using rays to determine points of intersection. Often used in lighting simulation.

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Platformer raycast collision detection

I'm using Unity to create a 2D platformer. For collision detection, I'm using raycasting to detect any possible collisions with specific collision layers, and adjusting the desired delta x & y ...
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212 views

Thick Ray interaction with AABB

I would like to intersect a thick ray (actually a cylinder) with an AABB. The current code to perform intersection with the ray is the following. template <class RealT> bool ...
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1answer
409 views

How can I ensure field of view symmetry in a Roguelike?

I'm working on a Roguelike, and for it I've created a ray-tracing/casting field-of-view (FoV) algorithm that consists of plotting Bresenham lines to every point in a solid circle. It's artifact free ...
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3answers
907 views

Strategy for detecting hits from a “cylinder ray”?

I was planning on using ray casting for collision detection in my game. However, when I use an attack similar to this: (which would project something like a cylinder), how would I go about ...
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1answer
510 views

Ray picking and bounding boxes in Java

How do I check which bounding boxes (of different types) a ray, sent from the camera through the mouse-click coordinates, intersects with first in Java (and where)? I have arrays (box_X, box_Y, box_Z, ...
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269 views

Block picking / ray casting through 3d blocks always slightly off

I've been working on adding a line-of-sight/ray-tracing system to my 3d block-world game. I've tried several different methods and they all work fairly well. At the moment I'm using something similar ...
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490 views

Are ambient, diffuse and specular light or material properties?

Are ambient, diffuse and specular properties of light or material? I am doing ray casting in OpenGL, I've managed to create lit sphere using formula I = L Ka + L Kd (n . l) + L Ks (r . v)^n but I ...
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box2d raycast filter category

I am trying to filter a category in my ray casting (jBox2D within libGDX), which should return the closest object that does not belong to the category LEVEL0. I've tried a plethora of approaches, but ...
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How to identify whether the boundingvolume intersects with walls or floor when it doesnt return normals?

My game in jMonkey is the kind that use will have to place objects in a scene (which consist of walls and slabs and floor). All my models are centered at origin. When the user click a point I use ray ...
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151 views

How to place an object so that it does not overlap the objects in my scene?

In my game, the user has to click at a point to place an object (mesh). I can cast a ray and find the horizontal point where the object can be translated and then attached to rootNode to display it. ...
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Corona SDK Live RayCasting [closed]

I'm looking for help involving rayCast in Corona SDK. If you haven't see it here's a link talking about it along with a demo. WEll in the demo you tap on a space and the ray is recasted and bounced if ...
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245 views

Volume raycaster problems HLSL

Hi this is my first question here so if I fail to include some necessary piece of information please dont rip my head off. ^^ I can't seem to get my volume raycaster to workt properly. I've been ...
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How to check whether a ray cast hits a specific side of an object?

I am using Ogre3d to develop a 3d simulation/game. One task is to determine whether the user has focused the camera on a specific object. So I cast a ray from the camera to what is currently in the ...
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1answer
128 views

3D drawing precision problem. XNA

I have a simple scrolling camera positioned 2000 units about the 3D 'floor' that moves forward by 1 unit every frame and looks down on the floor at a point that also moves forward by 1 unit every ...
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677 views

How can I remove the view and projection matrix from ray position to get only the ray model?

I've got a little problem with my picking module and I need your help. I have a method to project a ray from the camera to a fixed point when I click somewhere. The computed ray looks good, it go to ...
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152 views

Ray picking gives inversed results

I'm trying to do a simple ray picking implementation to allow a user to select a cell in a grid rendered in 3D. I'm almost there, but I've ran into an issue which I can't seem to solve. Consider the ...
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How do I implement occluded lighting in a block-based 2D game?

I want to have 2D lighting that can be blocked by in-game objects. My game has a top-down view and all game objects are described by rectangles. Let's say I have a 10x10 world and I place a light at ...
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593 views

Diagonal line of sight with two corners

Right now I'm using Bresenham's line algorithm for line of sight. The problem is I've found an edge case where players can look through walls. Occurs when the player looks between two corners of a ...
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1answer
281 views

Quick 3D sight calculation algorithm

I have a tile based board game where units move in 3D space on a 2D isometric view. When calculating attack tiles for a unit, how do I verify that they aren't shooting through a wall or a level too ...
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1answer
1k views

Ray Tracing in 3D - generating a ray

A ray is shot from the camera eye to the camera screen at point (i,j) how do I get the coordinates of that point in 3D world coordinates? The best I could find online is for point S S = Q + au + bv ...
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3answers
253 views

Keeping raycast on the same level

I want my raycast to end at certain height(red line). But as the game is 3D and the camera rotates I can't use a fixed magnitude. What I thought was a stroke of genius, I figured I'd project the ...
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2answers
615 views

Displaying sprites in a 2.5D raycasting engine

I'm developing a raycasting engine like the one used in DOOM, Wolfenstein 3D, etc. My engine is capable of correctly displaying walls and textures on walls, but I'm stuck at sprites rendering. Given ...
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More efficient way to implement Line of sight on a 2d grid with ray casting?

Consider a 2d grid of tiles, and an approximated sphere of coordinates - centered on the player - that represents line of sight. The goal is to block the line of sight beyond obstacles (ie walls). ...
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4answers
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Cast ray to select block in voxel game

I am developing a game with a Minecraft-like terrain made out of blocks. Since basic rendering and chunk loading is done now, I want to implement block selecting. Therefore I need to find out what ...
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1answer
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Raycasting “fisheye effect” question

Continuing my exploration of raycasting, I am very confused about how the correction of the fisheye effect works. Looking at the screenshot below from the tutorial at permadi.com, the way I ...
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Performance issues with visibility detection and object transparency

I'm working on a 3d game that has a view similar to classic isometric games (diablo, etc.). One of the things I'm trying to implement is the effect of turning walls transparent when the player walks ...
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1answer
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Raycasting tutorial / vector math question

I'm checking out this nice raycasting tutorial at http://lodev.org/cgtutor/raycasting.html and have a probably very simple math question. In the DDA algorithm I'm having trouble understanding the ...
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Narrow-phase collision detection algorithms

There are three phases of collision detection. Broadphase: It loops between all objecs that can interact, false positives are allowed, if it would speed up the loop. Narrowphase: Determines whether ...
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1answer
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Problems implementing a screen space shadow ray tracing shader

Here I previously asked for the possibility of ray tracing shadows in screen space in a deferred shader. Several problems were pointed out. One of the most important problem is that only visible ...
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2answers
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Raycasting mouse coordinates to rotated object?

I am trying to cast a ray from my mouse to a plane at a specified position with a known width and length and height. I know that you can use the NDC (Normalized Device Coordinates) to cast ray but I ...
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2answers
479 views

Wavefront mesh: determine which face a point belongs to?

I have a 3D mesh Wavefront .obj file. Is there any algorithm that takes an arbitrary point coordinates as input and determines which face of the mesh that point belongs to ?? The mesh is rendered on ...
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1answer
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Ray casting on a mesh using libgdx [closed]

I'm trying to perform ray casting on a mesh using libgdx. I found this code sample and it misses some explanations. What do these vectors stand for? What is globalIntersection and localIntersection?
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1answer
229 views

Looking for a library to create a grid based first person game online

Before I go and build it myself, I have been looking for a library that may help making a grid based first person view similar to: https://www.youtube.com/watch?v=GwmZoCFd4Us I plan to make a web ...
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Why doesn't Unity's OnCollisionEnter give me surface normals, and what's the most reliable way to get them?

Unity's on collision event gives you a Collision object that gives you some information about the collision that happened (including a list of ContactPoints with hit normals). But what you don't get ...
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1answer
401 views

OpenGL 3+ Range Picking

How do I perform range picking in the latest OpenGL version? By range picking I mean selecting all objects which are picked using a selection rectangle, like in an RTS game. For single object picking ...
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2answers
6k views

How to handle 3D collisions using raycasting (with a reflection vector?)

I'm making a game using THREE.JS, and I want my character to walk on the terrain, and collide with static 3D objects (=AABB boxes) that are on that terrain. The problem is: THREE.JS has only a ...
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1answer
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Raycasting Collision Detection

I need to check for collisions when firing a bullet, but I have a few questions first. My game is 2D and tile based, it also uses the XNA framework. From what I've read raycasting or continuous ...
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1answer
140 views

Is it safe to cast my 2D points to 3D points for a library which only takes Vector3s?

I need to cast a ray in 2D space for bullet collision detection, but the Ray.Intersects method requires a BoundingBox which uses vector3's not vector2's. My question is should I just ignore the Z ...
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1answer
699 views

What is an easy way to work subsurface scattering into a raycaster?

I've got some neat effects with path tracing: I want to add in an ability to do subsurface scattering, but I'm unsure of the general algorithm. With path tracing, it's: foreach pixel: trace( ...
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2answers
633 views

What mathematics would I need to know in order to build a 2.5D raycasting engine

I realize this is a fairly common-type question, but I've been studying Maths in my spare time, fairly slowly at that, and I really want to develop a raycasting engine like the original DOOM. I know ...
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1answer
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Finding if a point is inside of a mesh (Point-in-polyhedron)

How can I find if a point (Vector3) is inside of a mesh? Would this work for both concave and convex objects? I read somewhere that if you raycast in both directions of every axis (X, -X, Y, -Y, Z, ...
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2answers
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3D collision detection with meshes using only raycasting?

I'm building a game using WebGL and Three.js, and so far I have a terrain with a guy walking on it. I simply cast a ray downwards to know the terrain height. How can I do this for other 3D objects, ...
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1answer
398 views

3d Picking under reticle

i'm currently trying to work out some 3d picking code that I started years ago, but then lost interested the assignment was completed (this part wasn't actually part of the assignment). I am not ...
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1answer
532 views

How to calculate the viewing cone radius at a distance in raymarching?

I'm "raymarching distance fields" (proper lingo: sphere-tracing) in GLSL. To implement cone-marching atop of it (and also to minimize the number of raymarching steps regardless of whether ...
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1answer
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Optimized algorithm for line-sphere intersection in GLSL

Well, hello then! I need to find intersection between line and sphere in GLSL. Right now my solution is based on Paul Bourke's page and was ported to GLSL this way: // The line passes through p1 and ...
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How can I draw an arrow at the edge of the screen pointing to an object that is off screen?

I am wishing to do what is described in this topic: http://www.allegro.cc/forums/print-thread/283220 I have attempted a variety of the methods mentioned here. First I tried to use the method ...
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1answer
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OpenGL ES 2.0 gluUnProject

I've spent more time than I should trying to get my ray picking program working. I'm pretty convinced my math is solid with respect to line plane intersection, but I believe the problem lies with the ...
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Skewed: a rotating camera in a simple CPU-based voxel raycaster/raytracer

TL;DR — in my first simple software voxel raycaster, I cannot get camera rotations to work, seemingly correct matrices notwithstanding. The result is skewed: like a flat rendering, correctly rotated, ...
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4answers
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Ray Triangle Intersection issue

I'm trying to perform ray triangle intersection on a mesh made of triangles. The below code seems to work fine but only about 50% of the time. The ray often gets into positions where no intersection ...
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1answer
489 views

Raymarching artifacts

I was playing with raymarching using distance fields in GLSL sandbox and got stuck with a strange problem with artifacts. Click here and take a look at the spheres generated in corners, they have ...