# Glsl sphere

It also defines the means by which users can define types. Basic types in GLSL are the most fundamental types. Non-basic types are aggregates of these fundamental types. Each of the scalar types, including booleans, have 2, 3, and 4-component vector equivalents.

The n digit below can be 2, 3, or Vector values can have the same math operators applied to them that scalar values do. These all perform the component-wise operations on each component.

However, in order for these operators to work on vectors, the two vectors must have the same number of components. This is called swizzling. You can use x, y, z, or w, referring to the first, second, third, and fourth components, respectively. You can use any combination of up to 4 of the letters to create a vector of the same basic type of that length.

So otherVec. Any combination of up to 4 letters is acceptable, so long as the source vector actually has those components. Attempting to access the 'w' component of a vec3 for example is a compile-time error. However, when you use a swizzle as a way of setting component values, you cannot use the same swizzle component twice.

So someVec. Additionally, there are 3 sets of swizzle masks. You can use xyzwrgba for colorsor stpq for texture coordinates. These three sets have no actual difference; they're just syntactic sugar.

You cannot combine names from different sets in a single swizzle operation. In OpenGL 4. They obviously only have one source component, but it is legal to do this:. In addition to vectors, there are also matrix types. All matrix types are floating-point, either single-precision or double-precision. Matrix types are as follows, where n and m can be the numbers 2, 3, or I chose to write this tutorial, because I did not like the way you could and could not texture the sphere created by GLUT and when I looked on the internet, I could not find any tutorials on it.

The advantage of our sphere, is that we can set texture coordinates and if need be, place it inside either a display list, vertex array, or vertex buffer object, allowing us to call alot more than in immediate mode. This here will hold the information of all our vertices, such as x, y and z coordinates along with texture coordinates. Next we are going to use PI to convert our angles in degrees to radians. This here is going to determine how far apart each of our vertices are the further apart, the faster the program, but the squarer the sphere.

I chose 10 because it looks nice, and runs excellent. This will hold out total amount of vertices. Now we set up how many vertices we are going to use. Here I am enabling depth testing, texturing and face culling.

The depth testing is so that we acctually have depth to our scene, the texturing is so that we can apply textures to our sphere, and culling to used to speed up the application.

I have set the front face for culling to Counter Clock Wise, as triangle strips cull the opposite face to most other shapes.

Now we load our texture to be used. Now we call to create the sphere, I do not know why it does this, but the first input seems to choose how many subdivisions to perform. The next lets you choose where to move the sphere on the x, y and z axis. CreateSphere 70,0,0,0. Now for the actual creation code. We are inputting R as the number of subdivisions, H as the translation on the horizontal axis, K as the translation on the vertical axis, and Z as the translation on the Z axis.

While a and b are used to control our loops. Start editing our vertex. I am calculating the X value here. Hence Then we do the same calculations as before, only adding the space variable to the b values. Then we do the same calculations as the first, only adding the space variable to the a values.

Then we do the same calculations as the first again, only adding the space variable to both the b and the a values. To display the sphere I am calling this funtion which will set the size of it to 5 and assign the texture specified. DisplaySphere 5, texture[0] .No external assets images, sound clips, etc. Keep in mind that the executable also contains the code to generate the music. One of the techniques used in many demo scenes is called ray marching.

Signed distance functions, or SDFs for short, when passed the coordinates of a point in space, return the shortest distance between that point and some surface. The sign of the return value indicates whether the point is inside that surface or outside hence signed distance function.

## 31. OpenGL Sphere Creation

Consider a sphere centered at the origin. Points inside the sphere will have a distance from the origin less than the radius, points on the sphere will have distance equal to the radius, and points outside the sphere will have distances greater than the radius.

Using the Euclidean normthe above SDF looks like this:. Once we have something modeled as an SDF, how do we render it? This is where the ray marching algorithm comes in! Just as in raytracing, we select a position for the camera, put a grid in front of it, send rays from the camera through each point in the grid, with each grid point corresponding to a pixel in the output image.

The difference comes in how the scene is defined, which in turn changes our options for finding the intersection between the view ray and the scene. In raytracing, the scene is typically defined in terms of explicit geometry: triangles, spheres, etc. To find the intersection between the view ray and the scene, we do a series of geometric intersection tests: where does this ray intersect with this triangle, if at all?

To find the intersection between the view ray and the scene, we start at the camera, and move a point along the view ray, bit by bit. We hit something. Instead of taking a tiny step, we take the maximum step we know is safe without going through the surface: we step by the distance to the surface, which the SDF provides us! The blue line lies along the ray direction cast from the camera through the view plane.

The first step taken is quite large: it steps by the shortest distance to the surface. Combining that with a bit of code to select the view ray direction appropriately, the sphere SDF, and making any part of the surface that gets hit red, we end up with this:. The code is commented, so you should go check it out and experiment with it. To get to the code, hover over the image above, and click on the title. Most lighting models in computer graphics use some concept of surface normals to calculate what color a material should be at a given point on the surface.

When surfaces are defined by explicit geometry, like polygons, the normals are usually specified for each vertex, and the normal at any given point on a face can be found by interpolating the surrounding vertex normals. So how do we find surface normals for a scene defined by a signed distance function? We take the gradient! This will be our surface normal.

So the direction at the surface which will bring you from negative to positive most rapidly will be orthogonal to the surface. But no need to break out the calculus chops here. Armed with this knowledge, we can calculate the normal at any point on the surface, and use that to apply lighting with the Phong reflection model from two lights, and we get this:.

By default, all of the animated shaders in this post are paused to prevent it from making your computer sound like a jet taking off. Hover over the shader and hit play to see any animated effects. Just as in raytracing, for transformations on the camera, you transform the view ray via transformation matrices to position and rotate the camera.

Constructive solid geometry, or CSG for short, is a method of creating complex geometric shapes from simple ones via boolean operations. It turns out these operations are all concisely expressible when combining two surfaces expressed as SDFs.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I am trying to shade a sphere.

### Ray Marching and Signed Distance Functions

I have no idea where to start from. Here is some of my code:. Basically you need to calculate the lighting in vertex shader and pass the vertex color to the fragment shader if you want a per-vertex lighting or pass the normal and light direction as the varying variables and calculate everything there for the per-pixel lighting.

The main trick here is that when you pass the normal to the fragment shader it is being interpolated between vertices for each fragment and as the result the shading is very smooth but also slower. Here is a very nice article to start with. Learn more. Asked 8 years, 5 months ago. Active 8 years, 5 months ago.

Viewed 3k times. From are the Sphere's Normal Vertices.

Coding Challenge #25: Spherical Geometry

Trt Trt Trt Trt 4, 10 10 gold badges 43 43 silver badges 70 70 bronze badges. Have you considered learning OpenGL by following a tutorial?

It would be a lot easier on you than asking large, complex questions like "how do I do lighting? Active Oldest Votes. Nicol Bolas k 44 44 gold badges silver badges bronze badges.

Animal Crossing Shaders. This shaderpack maps the local terrain onto a sphere, similar to the Animal Crossing games. Like the Acid Shaders they are based entirely on vertex transformations, and should yield little, if any, performance loss.

Acid Shaders r6 for Minecraft 1. Animal Crossing Shaders r6 for Minecraft 1. Acid Shaders r5 for Minecraft 1. Animal Crossing Shaders r5 for Minecraft 1. Acid Shaders Screen Space r4 for Minecraft 1. Acid Shaders World Space r4 for Minecraft 1. Gaeel - Creating the original version of the Acid Shaders Sildur - Indirectly showing me how the newer versions of Shaders work. My links:.

Screen space and world space refer to the geometric space in which the deformations are applied. The world space edition is new, and warps the world around the player, instead of around where the player is looking.

## 31. OpenGL Sphere Creation

This means that the terrain is no longer morphed around as you change your camera's viewing angle of the world. The "de-spawning chunks" bug is more prevalent in the world space edition. Fixed the block outline bug. Forked the shaders into 2 different releases, "Screen Space" and "World Space". These titles pertain to how the deformations are applied to the terrain.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

Game Development Stack Exchange is a question and answer site for professional and independent game developers. It only takes a minute to sign up. I believe if I draw it using some primitives like circle it would be very slow drawing thousand of circles every frame would be too expensive even in pure opengl. So I've decided to write a small shader for that purpose. It should be pretty simple, but I don't even know where to start.

I'm completely new to shader programming. I know how to run shader program, the basic terms, etc, so, for example, I can draw a circle on a screen with given radius, nothing more. Can you, please, tell me where to start? I've searched shadertoy, but can't find any suitable example.

I believe it should be pretty easy to write this, may be I'm just missing some conceptions. Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Asked 2 years, 3 months ago. Active 2 years, 3 months ago. Viewed times. Thanks in advance. It does exactly what you propose "would be very slow": plotting each star as its own independent primitive, and it seems to run fine on my several-years-old phone.

So you might be optimizing prematurely here. If you want to proceed with a shader-based approach, can you outline at least a little about the strategy you want to use? I can probably achieve that using particles system, but then particles will be just pixels points where I want it to be a small primites e.

Here the code :. Here are some facts why:. This, and considering that you want to draw millions of these spheres, means that your card can easily get to its rasterization throughput limit. Even if rasterization throughput is not clamping your performance, rasterizing the additional triangles will degrade performance anyway as more data has to be processed.

Geometry shaders do not perform well when emitting loads of vertices. This is because those vertices has to be stored first in a temporary buffer which limits the number of parallel cores that execute your geometry shader.

But any card will suffer heavily from this. You need some cycles in your geometry shaders to construct a sphere geometry, which is not really parallel. Instanced geometry shaders introduced by GL4. My main question is why you want to go with a geometry shader based solution if you have your point sprite based solution up and running? The later one should be orders of magnitude faster.

Btw, looking at your geometry shader it barely looks like something that creates a sphere geometry, rather it looks like a geometry shader that is meant to emit point sprites or billboards, whatever you call them, just there is some strange for cycle at the beginning which emits the received vertices. It all looks weird.

Pulling off a textured sphere impostor requires selecting texture coordinates based on the view direction for that fragment. I would be more than happy to apply it correctly :!

Do you have some example of code for doing this? Here a picture of my actual project. Just as the camera rotates, rotate the uniform having light direction vector! Here two texture i found. Someone told me i could use them to transform the point sprite in real spheres using shaders.

Anyone can help me with this? Geometry shader, point sprite to sphere OpenGL. But any card will suffer heavily from this You need some cycles in your geometry shaders to construct a sphere geometry, which is not really parallel. ZbuffeR March 17,pm 5.

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