I'm using the following vertex shader (courtesy http://stemkoski.github.io/Three.js/Shader-Heightmap-Textures.html) to generate terrain from a grayscale height map:
uniform sampler2D bumpTexture;
uniform float bumpScale;
varying float vAmount;
varying vec2 vUV;
void main()
{
vUV = uv;
vec4 bumpData = texture2D( bumpTexture, uv );
vAmount = bumpData.r; // assuming map is grayscale it doesn't matter if you use r, g, or b.
// move the position along the normal
vec3 newPosition = position + normal * bumpScale * vAmount;
gl_Position = projectionMatrix * modelViewMatrix * vec4( newPosition, 1.0);
}
I'd like to have 32-bits of resolution, and have generated a heightmap that encodes heights as RGBA. I have no idea how to go about changing the shader code to accommodate this. Any direction or help?
bumpData.r, .g, .b and .a are all quantities in the range [0.0, 1.0] equivalent to the original byte values divided by 255.0.
So depending on your endianness, a naive conversion back to the original int might be:
(bumpData.r * 255.0) +
(bumpdata.g * 255.0 * 256.0) +
(bumpData.b * 255.0 * 256.0 * 256.0) +
(bumpData.a * 255.0 * 256.0 * 256.0 * 256.0)
So that's the same as a dot product with the vector (255.0, 65280.0, 16711680.0, 4278190080.0), which is likely to be the much more efficient way to implement it.
With threejs
const generateHeightTexture = (width) => {
// let max_texture_width = RENDERER.capabilities.maxTextureSize;
let pixels = new Float32Array(width * width)
pixels.fill(0, 0, pixels.length);
let texture = new THREE.DataTexture(pixels, width, width, THREE.AlphaFormat, THREE.FloatType);
texture.magFilter = THREE.LinearFilter;
texture.minFilter = THREE.NearestFilter;
// texture.anisotropy = RENDERER.capabilities.getMaxAnisotropy();
texture.needsUpdate = true;
console.log('Built Physical Texture:', width, 'x', width)
return texture;
}
Related
Im in a Three.js project and Im trying to convert a square with a square texture inside into a trapezoid.
I manage to create the shape but the texture inside, although it fits/cover the shape it do it with an undesired distorsión.
Im using a PlaneBufferGeometry with ShaderMaterial and im trying to obtain this distorsion in the shader part (although it would be ok if it is done in the threejs geometry part).
This is my vertex:
uniform sampler2D uTexture;
varying vec2 vUv;
void main(){
float scaleTOP = 0.5;
float scaleBOTTOM = 1.0;
float scaleLEFT = 1.0;
float scaleRIGHT = 1.0;
float scaleX = mix(scaleBOTTOM, scaleTOP, uv.y);
float posX = position.x*scaleX;
float scaleY = mix(scaleLEFT, scaleRIGHT, uv.x);
float posY = position.y*scaleY;
vec3 finalPosition = vec3(posX, posY);
gl_Position = projectionMatrix * modelViewMatrix * vec4( finalPosition, 1.0 );
// Varyings:
vUv = uv;
}
And this is my fragment:
uniform sampler2D uTexture;
varying vec2 vUv;
void main() {
vec4 tex = texture2D ( uTexture, vUv );
gl_FragColor = vec4(tex.r, tex.g, tex.b, 1.0);
}
Unfortunately I manage to distort the square into the trapezoid but the texture is not distorted in the way I want. See figure to see the intended result:
Figure:
My vertex and fragment were ok.
The problem was that the Threejs geometry I was using had only 2 polygons. I was using:
this.bg_geometry = new THREE.PlaneBufferGeometry(width, height, 1, 1)
Thats it... with only one division which only created two triangles which actually can be seen in the figure I posted.
I changed the geometry to:
this.bg_geometry = new THREE.PlaneBufferGeometry(width, height, 100, 100)
...and now the texture is distorted as desired.
Anyway many thanks to #prisoner849 as he put me in the track to pass 4 points as uniforms uPoints in this order: TL,TR,BL,BR to set the shape of the plane.
My vertex shader looks now like this:
uniform vec3 uPoints[4];
varying vec2 vUv;
void main(){
vec3 baselineBottom = (uPoints[3] - uPoints[2]) * uv.x + uPoints[2];
vec3 baselineTop = (uPoints[1] - uPoints[0]) * uv.x + uPoints[0];
vec3 finalPosition = (baselineTop - baselineBottom) * uv.y + baselineBottom;
gl_Position = projectionMatrix * modelViewMatrix * vec4( finalPosition, 1.0 );
vUv = uv;
}
My goal is to draw a circle around my mouse cursor over a plane.
I get NDC coordinates (-1 to +1) that represent my cursor position:
const rect = targetHTML.getBoundingClientRect();
const mousePositionX = event.clientX - rect.left;
const mousePositionY = event.clientY - rect.top;
this._currentPoint = {
x: (mousePositionX / targetHTML.clientWidth * 2 - 1),
y: (mousePositionY / targetHTML.clientHeight * -2 + 1),
};
I pass it to my fragment shader via uniforms:
this._cursorMaterial.uniforms.uBrushPosition.value =
new window.THREE.Vector2(this._currentPoint.x, this._currentPoint.y);
In my fragment shader, I want to convert it to a world coordinate in order to compare it to the fragment world location.
// vertex shader
varying vec4 vPos;
void main() {
vPos = modelMatrix * vec4(position, 1.0 );
gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1.0 );
}
// fragment shader
varying vec4 vPos;
uniform vec2 uBrushPosition;
void main() {
// convert uBrush position to world space
// uBrushPosition
vec3 brushWorldPosition = ?
//
if (distance(brushWorldPosition, vpos) < 10.) {
gl_FragColor = vec4(1., 0., 0., .5);
}
discard;
Not in the shader, but you can send it in as a uniform.
var mouseWorld = new THREE.Vector3( mouse.x, mouse.y, distanceFromCamera )
mouseWorld.unproject( camera )
I am trying to tweak this ShaderToy example for vertices to create 'sparks'
out of them. Have tried to play with gl_PointCoord and gl_FragCoord without any results. Maybe, someone here could help me?
I need effect similar to this animated gif:
uniform float time;
uniform vec2 mouse;
uniform vec2 resolution;
#define M_PI 3.1415926535897932384626433832795
float rand(vec2 co)
{
return fract(sin(dot(co.xy ,vec2(12.9898,78.233))) * 43758.5453);
}
void main( ) {
float size = 30.0;
float prob = 0.95;
vec2 pos = floor(1.0 / size * gl_FragCoord.xy);
float color = 0.0;
float starValue = rand(pos);
if (starValue > prob)
{
vec2 center = size * pos + vec2(size, size) * 0.5;
float t = 0.9 + sin(time + (starValue - prob) / (1.0 - prob) * 45.0);
color = 1.0 - distance(gl_FragCoord.xy, center) / (0.5 * size);
color = color * t / (abs(gl_FragCoord.y - center.y)) * t / (abs(gl_FragCoord.x - center.x));
}
else if (rand(gl_FragCoord.xy / resolution.xy) > 0.996)
{
float r = rand(gl_FragCoord.xy);
color = r * ( 0.25 * sin(time * (r * 5.0) + 720.0 * r) + 0.75);
}
gl_FragColor = vec4(vec3(color), 1.0);
}
As I understand have to play with vec2 pos, setting it to a vertex position.
You don't need to play with pos. As Vertex Shader is only run by each vertex, there is no way to process its pixel values there using Pos. However, you can do processing pixel using gl_PointCoord.
I can think of two ways only for changing the scale of a texture
gl_PointSize in Vertex Shader in opengl es
In Fragment Shader, you can change the texture UV value, for example,
vec4 color = texture(texture0, ((gl_PointCoord-0.5) * factor) + vec2(0.5));
If you don't want to use any texture but only pixel processing in FS,
you can set UV like ((gl_PointCoord-0.5) * factor) + vec2(0.5)
instead of uv which is normally set as fragCoord.xy / iResolution.xy in Shadertoy
I'm changing the z coordinate vertices on my geometry but find that the Mesh Stays the same size, and I'm expecting it to get smaller. Tweening between vertex positions works as expected in X,Y space however.
This is how I'm calculating my gl_Position by tweening the amplitude uniform in my render function:
<script type="x-shader/x-vertex" id="vertexshader">
uniform float amplitude;
uniform float direction;
uniform vec3 cameraPos;
uniform float time;
attribute vec3 tweenPosition;
varying vec2 vUv;
void main() {
vec3 pos = position;
vec3 morphed = vec3( 0.0, 0.0, 0.0 );
morphed += ( tweenPosition - position ) * amplitude;
morphed += pos;
vec4 mvPosition = modelViewMatrix * vec4( morphed * vec3(1, -1, 0), 1.0 );
vUv = uv;
gl_Position = projectionMatrix * mvPosition;
}
</script>
I also tried something like this from calculating perspective on webglfundamentals:
vec4 newPos = projectionMatrix * mvPosition;
float zToDivideBy = 1.0 + newPos.z * 1.0;
gl_Position = vec4(newPos.xyz, zToDivideBy);
This is my loop to calculate another vertex set that I'm tweening between:
for (var i = 0; i < positions.length; i++) {
if ((i+1) % 3 === 0) {
// subtracting from z coord of each vertex
tweenPositions[i] = positions[i]- (Math.random() * 2000);
} else {
tweenPositions[i] = positions[i]
}
}
I get the same results with this -- objects further away in Z-Space do not scale / attenuate / do anything different. What gives?
morphed * vec3(1, -1, 0)
z is always zero in your code.
[x,y,z] * [1,-1,0] = [x,-y,0]
In effort to learn vertex/fragment shaders I decided to create a simple rain effect by updating the y position of a point in the vertex shader and resetting it back to animate through again using Three.js PointCloud. I got it to animate across the screen once but gets stuck after resetting the y position.
uniform float size;
uniform float delta;
varying float vOpacity;
varying float vTexture;
void main() {
vOpacity = opacity;
vTexture = texture;
gl_PointSize = 164.0;
vec3 p = position;
vec3 p = position;
p.y -= delta * 50.0;
vec4 mvPosition = modelViewMatrix * vec4(1.0 * p, 1.0 );
vec4 nPos = projectionMatrix * mvPosition;
if(nPos.y < -200.0){
nPos.y = 100.0;
}
gl_Position = nPos;
}
Any ideas? Thanks
shader does not change the vertex position permanently
that means
gl_Position = nPos;
will not propagate to your position attribute in geometry
shader only runs on graphics card and has no access to memory of the browser
you can change your code to this:
nPos.y = mod(nPos.y, 300.0) - 200.0;
now the y coordinate should change as you want it to(going from 100 to -200 then back to 100)