Figure 1: Simplified representation of a raytracer. However, of course, it would be hard to actually use raymarched objects in a game without being able to light them (except, I guess, in some sort of abstract game).To perform any sort of lighting calculation of an object, you must first calculate the normals of that object. Therefore// If the sample <= 0, we have hit something (see map()).// If t > drawdist, we can safely bail because we have reached the max draw distance// Simply return the number of steps taken, mapped to a color ramp.// By this point the loop guard (i < maxstep) is false. This way it is possible to find which objects the ray intersects (that is, the objects that the camera sees). However, you run into a major problem very quickly: Mesh-based objects and raymarched objects can’t interact with or touch each other! Raymarching Distance Fields: Concepts and Implementation in Unity. If the given point (point p) is inside of an object, we return a// If the sample <= 0, we have hit something (see map()).// Simply return a gray color if we have hit an object// If the sample > 0, we haven't hit anything yet so we should march forward// We step forward by distance d, because d is the minimum distance possible to intersect// epsilon - used to approximate dx when taking the derivative// The idea here is to find the "gradient" of the distance field at pos// Remember, the distance field is not boolean - even if you are inside an object// the number is negative, so this calculation still works.// Essentially you are approximating the derivative of the distance field at this point.// If the sample <= 0, we have hit something (see map()).// If the sample > 0, we haven't hit anything yet so we should march forward// We step forward by distance d, because d is the minimum distance possible to intersect// Therefore multiplying the ray by some number i gives the viewspace position// If we run past the depth buffer, stop and return nothing (transparent pixel)// this way raymarched objects and traditional meshes can coexist.// Convert from depth buffer (eye space) to true distance from camera// This is done by multiplying the eyespace depth by the length of the "z-normalized"// ray (see vert()). Manual said in that case to use "Post Processing -> Color Grading tonemapping" but there is no such feature in Unity 2017. Raymarching does not try to directly calculate this intersection analytically. Contribute to smkplus/UnityRayMarching development by creating an account on GitHub. In fact, the raymarched objects To fix this problem, we need to find the distance along each ray at which the closest mesh-based object lies. To do this, you simply need to take advantage of some simple distance field combine operations: You can extend your distance field function to return material data as well. Because of this, much of the C# code that we will write is similar to what you would use for a full-screen image effect.Let’s implement a basic image effect loading script.

Additionally you can not raytrace through volumetric materials, such as clouds and water. Note that we are storing// our own custom frustum information in the z coordinate.// Remember, the z value here contains the index of _FrustumCornersES to use// Output of vertex shader / input to fragment shader// Index passed via custom blit function in RaymarchGeneric.cs// Note: _CameraInvViewMatrix was provided by the script// Adapted from: http://iquilezles.org/www/articles/distfunctions/distfunctions.htm// This is the distance field function. The pixels that do not show any raymarched objects (most pixels fall under this category) display the maximum step size! In a raytracer, you are given a set of equations that determine the intersection of a ray and the objects you are rendering. It is also possible to render nonpolygonal objects such as spheres because you only need to know the sphere / ray intersection formula (for example). This makes sense: the rays cast from these pixels never hit anything, so they march onward forever.

The issue with clouds and sky which is too over-bright. However, below are some simple techniques that I have tried out. This loop will be called from the fragment shader, and as explained at the top of this post, is responsible for “marching” a sample point along the current pixel’s ray. The depth buffer is accessible to all image effects shaders and stores the Now we need to make some modifications to our code to align with the above theory. We can add this optimization to a normal raymarch loop by adding the draw distance check to the depth buffer culling check:I hope that this article has given a fairly robust introduction to Distance Field Raymarching. My research so far: The original article suggest two pass rendering of particles for each voxel, in first pass reading output after each particle(!) Think of similar triangles: the view-space z-distance between a point// and the camera is proportional to the absolute distance.// Adapted from: http://iquilezles.org/www/articles/distfunctions/distfunctions.htm// Adapted from: http://iquilezles.org/www/articles/distfunctions/distfunctions.htm// Adapted from: http://iquilezles.org/www/articles/distfunctions/distfunctions.htm// Adapted from: http://iquilezles.org/www/articles/distfunctions/distfunctions.htm// If the sample <= 0, we have hit something (see map()).// Use y value given by map() to choose a color from our Color Ramp// If the sample <= 0, we have hit something (see map()).// Simply return the number of steps taken, mapped to a color ramp.// By this point the loop guard (i < maxstep) is false. The thick black line is an example ray cast to render a pixel from the camera. In order to pass a light source to our shader, we need to modify our scripts a bit:These additions simply pass along a vector to our shader that describes the direction of the sun. Once again you can find a complete reference implementation at /// \brief Stores the normalized rays representing the camera frustum in a 4x4 matrix. is rendered.This approach is both slow and outdated not leveraging modern shader pipeline in addition to being overly complicated. This vector is passed to our scripts by the shader uniform So now you have constructed a bunch of objects using distance fields and you are ready to integrate them into your Unity project. We also want these rays to match up with the Unity render settings (such as the camera’s postion, rotation, FOV, etc).There are many ways of doing this, but I have chosen to use the following procedure every frame:To calculate the camera frustum corner rays, you have to take into account the field of view of the camera as well as the camera’s aspect ratio.

More concretely, any It turns out that, at any point on a surface defined in the distance field, the Be careful however, because this technique is quite expensive! To remedy this performance issue, we can add a maximum draw distance like so:Much better!