I want to change the color of the strokes but I can't figure out how to do this correctly I looked up a tutorial and it showed me the hu stuff in the code. That it changes the hu in the for loop but it just remains one color.. In my case yellowish
void setup(){
size(500,500);
colorMode(HSB);
}
float t = 0;
float tn = 0;
void draw(){
background(0);
translate(width / 2, height / 2);
noFill();
stroke(255);
strokeWeight(2);
float hu = 0;
beginShape();
//add vertices...
for(float theta = 0; theta <= 8 * PI; theta += 0.001){
float rad = r(theta,
1, //a
1, //b
sin(tn) * 0.1 + 5, //m
cos(tn) / 2, //n1
sin(t) * 0.5 + 0.5, //n2
cos(t) * 0.5 + 0.5 //n3
);
float x = rad * cos(theta) * 50;
float y = rad * sin(theta) * 50;
stroke(hu, 255, 255);
vertex(x,y);
hu += 1;
if(hu > 255){
hu = 0;
}
}
endShape();
t += 0.1;
tn += 0.1;
}
float r(float theta, float a, float b, float m, float n1, float n2, float n3){
return pow(pow(abs(cos(m * theta / 4.0) / a), n2) +
pow(abs(sin(m * theta / 4.0) / b), n3), -1.0 / n1) ;
}
Please consult the Processing reference for the beginShape function:
The P2D and P3D renderers allow stroke() and fill() to be altered on a per-vertex basis, but the default renderer does not.
In other words, you can't change the stroke color like this with the default renderer. You could just use the P2D renderer instead:
size(500, 500, P2D);
If you need to use the default renderer for some reason, then you're going to have to draw the lines yourself instead of relying on the vertex function.
Related
I am learning opengl but having problem rendering sphere. I can draw and bind the texture of polygon normally but when I try to use the same method to the sphere drew by triangle strip, it just didn't went well. Part of the texture is broken. (Pic on below)
May I know what did I do wrongly? Sorry if this is an obvious question.
Here are the code of sphere :
(before adding the texture part, the sphere can be displayed normally)
private void drawSphere(GL gl) {
Position spherePosition = state.getSpherePosition();
final float PI = 3.141592f;
gl.glPushMatrix();
if(spheretexture == null){
setSphereTexture();
}
gl.glTranslated(spherePosition.getX(), spherePosition.getY(), spherePosition.getZ());
float[] ambientDiffuse = new float[] {255.0f, 255.0f, 255.0f, 1.0f};
gl.glMaterialfv(GL.GL_FRONT_AND_BACK, GL.GL_AMBIENT_AND_DIFFUSE, ambientDiffuse, 0);
gl.glEnable(GL_BLEND);
gl.glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
float x, y, z, alpha, beta; // Storage for coordinates and angles
float radius = 25f;
int gradation = 10;
for (alpha = 0.0f; alpha < PI; alpha += PI / gradation) {
spheretexture.enable();
spheretexture.bind();
gl.glBegin(GL_TRIANGLE_STRIP);
for (beta = 0.0f; beta < 2.01 * PI; beta += PI / gradation) {
x = (float) (radius * Math.cos(beta) * Math.sin(alpha));
y = (float) (radius * Math.sin(beta) * Math.sin(alpha));
z = (float) (radius * Math.cos(alpha));
gl.glTexCoord2f(beta / (2.0f * PI), alpha / PI);
gl.glVertex3f(x, y, z);
x = (float) (radius * Math.cos(beta) * Math.sin(alpha + PI / gradation));
y = (float) (radius * Math.sin(beta) * Math.sin(alpha + PI / gradation));
z = (float) (radius * Math.cos(alpha + PI / gradation));
gl.glTexCoord2f(beta / (2.0f * PI), alpha / PI + 1.0f / gradation);
gl.glVertex3f(x, y, z);
}
gl.glEnd();
spheretexture.disable();
gl.glDisable(GL_BLEND);
gl.glPopMatrix();
}
}
Output picture:
The major issue is that the top cap of the sphere is drawn twice. That causes Z-fighting. Note, first it is drawn buy the strip between PI-PI/gradation and PI and then it is drawn by the strip between PI and PI+PI/gradation. That is caused, because the outer loop does one an extra pass. Change it to:
for (alpha = 0.0f; alpha < PI-PI/gradation; alpha += PI / gradation) {
// [...]
}
or even better
for (int i = 0; i < gradation; ++ i ) {
float alpha = PI * (float)i / (float)(gradation);
// [...]
}
I have to points in 3D space that I want to draw a cylinder between. I currently have this code:
applet.pushMatrix();
applet.stroke(0);
applet.fill(0);
applet.line(this.start.x, this.start.y, this.start.z, this.end.x, this.end.y, this.end.z); //debug, shows where the cylinder should be
applet.translate(this.start.x, this.start.y);
applet.beginShape(PConstants.TRIANGLE_STRIP);
float xdif = this.end.x - this.start.x;
float ydif = this.end.y - this.start.y;
float zdif = this.end.z - this.start.z;
float rx = (float)Math.atan(ydif / xdif);
float ry = (float)Math.atan(zdif / xdif);
float rz = (float)Math.atan(zdif == 0 ? 0 : ydif / zdif);
applet.rotateZ((float) (rx - Math.PI / 2));
applet.rotateY((float) (ry - Math.PI / 2));
applet.rotateX((float) (rz - Math.PI / 2));
float r = 20;
float len = HelperFunctions.distance(this.start, this.end) / 2;
boolean w = false;
for (int i = 0; i < 2; i += 1) {
for (float j = 0; j < Math.PI * 2 + 0.2; j += 0.4) {
w = !w;
float z = (i + (w ? 0 : 1)) * len;
float x = (float)(r * Math.cos(j));
float y = (float)(r * Math.sin(j));
applet.vertex(y, x, z);
}
}
applet.endShape();
applet.popMatrix();
The cylinder does draw correctly, however, it doesn't rotate correctly. I'm trying to use trig to determine the rotation angles, however, I'm not sure I've done it correctly. How would I get the correct angles to rotate around such that it is drawn from Vector start to Vector end?
Vector is a custom class with just a float x, y, z, and HelperFunctions.distance takes two Vectors and calculates the distance (pythagoras).
Thanks in advance.
I am having a bit of trouble trying to figure out how to draw paths from a point on a canvas with the start of each path being equally distanced from the initial point. To illustrate what I mean, the code that I have so far is able to generate this:
and the desired result is something like this:
My code:
int n = 3;
int r;
double x;
double y;
point1 = new Point(mWidth/2, mHeight/2);
double angle;
double angleFactor;
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
for (int i = 0; i < 3; i++){
angleFactor = 2 * Math.PI / n;
angle = i * angleFactor;
x = (point1.x) + r * Math.cos(angle);
y = (point1.y) + r * Math.sin(angle);
//Draw paths
path.reset();
path.moveTo(point1.x, point1.y);
path.lineTo((float) x, (float) y);
canvas.drawPath(path, paint);
}
}
Is there a simple solution to this?
Since you want to have a tiny distance between the offset of a line and the center point, you can define start coordinates like this:
double xStart, xEnd;
double yStart, yEnd;
double offsetFraction = 0.1;
Inside the for loop in onDraw() :
double lengthX = r * Math.cos(angle);
double lengthY = r * Math.sin(angle);
xStart = (point1.x) + offsetFraction * lengthX;
yStart = (point1.y) + offsetFraction * lengthY;
xEnd = (point1.x) + lengthX;
yEnd = (point1.y) + lengthY;
//Draw paths
path.reset();
path.moveTo((float) xStart, (float) yStart);
path.lineTo((float) xEnd, (float) yEnd);
canvas.drawPath(path, paint);
(Question is at bottom)Im learning opengl(using lwjgl) and done some drawing of flat shape through sending buffers. Now I need to draw many spheres in single buffer. In my last question, I was advised to use geometry instancing but I dont know how to use any shader language in java yet so I'm trying to make multiple objects in single buffer just like in the examples.
What I tried to generate two spheres by QUAD_STRIP style(using lwjgl's own GLU.Sphere() function to fill the buffers):
n=c1*(c2+1);
float rr=(float) Math.random();
float gg=(float) Math.random();
float bb=(float) Math.random();
float aa=(float) Math.random();
positions = new float[c1 * (c2+1) * 3*2 *2];
normals = new float[c1 * (c2+1) * 3*2 *2];
colors = new float[c1 * (c2+1) * 4*2 *2];
int counter=0;
float drho = 3.141593F / 32.0f;
float dtheta = 6.283186F / 32.0f;
float ds = 1.0F / 32.0f;
float dt = 1.0F / 32.0f;
float t = 1.0F;
/*first sphere*/
for (int i = 0; i < 32; i++) {
float rho = i * drho;
float s = 0.0F;
for (int j = 0; j <= 32; j++) {
float theta = j == 32 ? 0.0F : j * dtheta;
float x = (float) (-Math.sin(theta) * Math.sin(rho));
float y = (float) (Math.cos(theta) * Math.sin(rho));
float z = (float) (1.0f * Math.cos(rho));
normals[counter*3+0]=x*1.0f;normals[counter*3+1]=y*1.0f;normalscounter*3+2]=z*1.0f;
colors[counter*4+0]=rr;colors[counter*4+1]=gg;colors[counter*4+2]=bb;colors[counter*4+3]=1.0f/*aa*/;
positions[counter*3+0]=x*r;positions[counter*3+1]=y*r;positions[counter*3+2]=z*r;
counter++;
x = (float) (-Math.sin(theta) * Math.sin(rho + drho));
y = (float) (Math.cos(theta) * Math.sin(rho + drho));
z = (float) (1.0f * Math.cos(rho + drho));
normals[counter*3+0]=x*1.0f;normals[counter*3+1]=y*1.0f;normals[counter*3+2]=z*1.0f;
colors[counter*4+0]=rr;colors[counter*4+1]=gg;colors[counter*4+2]=bb;colors[counter*4+3]=1.0f/*aa*/;
positions[counter*3+0]=x*r;positions[counter*3+1]=y*r;positions[counter*3+2]=z*r;
counter++;
s += ds;
}
t -= dt;
}
/* first sphere end */
/* second sphere generation */
{
drho = 3.141593F / 32.0f;
dtheta = 6.283186F / 32.0f;
ds = 1.0F / 32.0f;
dt = 1.0F / 32.0f;
t = 1.0F;
for (int i = 0; i < 32; i++) {
float rho = i * drho;
float s = 0.0F;
for (int j = 0; j <= 32; j++) {
float theta = j == 32 ? 0.0F : j * dtheta;
float x = (float) (-Math.sin(theta) * Math.sin(rho));
float y = (float) (Math.cos(theta) * Math.sin(rho));
float z = (float) (1.0f * Math.cos(rho));
normals[counter*3+0]=x*1.0f;normals[counter*3+1]=y*1.0f;normals[counter*3+2]=z*1.0f;
colors[counter*4+0]=rr;colors[counter*4+1]=gg;colors[counter*4+2]=bb;colors[counter*4+3]=1.0f/*aa*/;
positions[counter*3+0]=x*r+1.0f;positions[counter*3+1]=y*r+1.0f;positions[counter*3+2]=z*r+1.0f;
counter++;
x = (float) (-Math.sin(theta) * Math.sin(rho + drho));
y = (float) (Math.cos(theta) * Math.sin(rho + drho));
z = (float) (1.0f * Math.cos(rho + drho));
normals[counter*3+0]=x*1.0f;normals[counter*3+1]=y*1.0f;normals[counter*3+2]=z*1.0f;
colors[counter*4+0]=rr;colors[counter*4+1]=gg;colors[counter*4+2]=bb;colors[counter*4+3]=1.0f/*aa*/;
positions[counter*3+0]=x*r+1.0f;positions[counter*3+1]=y*r+1.0f;positions[counter*3+2]=z*r+1.0f;
counter++;
s += ds;
}
t -= dt;
}
}
/*second sphere end*/
positionsBuf=BufferUtils.createFloatBuffer(c1 * (c2+1) * 3*2 *2);
positionsBuf.put(positions);
positionsBuf.rewind();
colorsBuf=BufferUtils.createFloatBuffer(c1 * (c2+1) * 4*2 *2);
colorsBuf.put(colors);
colorsBuf.rewind();
normalsBuf=BufferUtils.createFloatBuffer(c1 * (c2+1) * 3*2 *2);
normalsBuf.put(normals);
normalsBuf.rewind();
As you can see, below image shows how two spheres are drawn. There is an unwanted link between two.
Most probably the rope is caused by the last point of first sphere and first point of second sphere. Is there some kind of delimiter/drawing-hint to separate two drawings in the same buffer?
Here is how they are drawn:
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER,sphereBufferCol.get(0));
GL11.glColorPointer(4, GL11.GL_FLOAT, 0, 0);
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, sphereBufferPos.get(0));
GL11.glVertexPointer(3, GL11.GL_FLOAT, 0, 0);
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, sphereBufferNormal.get(0));
GL11.glNormalPointer(GL11.GL_FLOAT, 0, 0);
GL11.glEnableClientState(GL11.GL_VERTEX_ARRAY);
GL11.glEnableClientState(GL11.GL_COLOR_ARRAY);
GL11.glEnableClientState(GL11.GL_NORMAL_ARRAY);
//Each sphere is generated 32 by 32 quadstriparray and each having two sets of two points and there are two spheres
GL11.glDrawArrays(GL11.GL_QUAD_STRIP, 0, 32*33*2 *2);
GL11.glDisableClientState(GL11.GL_VERTEX_ARRAY);
GL11.glDisableClientState(GL11.GL_COLOR_ARRAY);
GL11.glDisableClientState(GL11.GL_NORMAL_ARRAY);
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, 0);
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, 0);
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, 0);
Question: How can I make that rope-like thing disappear without decreasing performance? Maybe putting zero to last and first points' alpha value can make it invisible but wouldnt that cause two holes on each sphere and decrease performance because of many lines on the screen?
All vertex values will be altered by opencl interoperability so single drawing call is needed to draw whole 10000+ spheres.
There seem to be a number of options:
use multiple buffers
use quads instead of quad strips
use primitive restart
use degenerate triangles, i.e. add the last vertex twice
use [instanced rendering] (http://www.opengl.org/wiki/Vertex_Rendering#Instancing)
If you are on newer hardware and want to use quad strips, I'd prefer using primitive restart.
Please note that this is just the result of a quick assessment and anchecked (I personally don't use quad strips or even tri strips that often ;) ).
I created a class with a method drawSphere to replace glutDrawSolidSphere. See code below.
But I wonder, how do I wrap a texture around it without tiling? For example, if I want to draw a mouth, eyes and a nose on it, then I want it to have only one mouth, two eyes and one nose, and not 100 tiled all over the sphere.
I'm using Jogl with some libraries.
class Shape {
public void drawSphere(double radius, int slices, int stacks) {
gl.glEnable(GL_TEXTURE_2D);
head.bind(gl); //This method is a shorthand equivalent of gl.glBindTexture(texture.getTarget(), texture.getTextureObject());
gl.glBegin(GL_QUADS);
double stack = (2*PI)/stacks;
double slice = (2*PI)/slices;
for (double theta = 0; theta < 2 * PI; theta += stack) {
for (double phi = 0; phi < 2 * PI; phi += slice) {
Vector p1 = getPoints(phi, theta, radius);
Vector p2 = getPoints(phi + slice, theta, radius);
Vector p3 = getPoints(phi + slice, theta + stack, radius);
Vector p4 = getPoints(phi, theta + stack, radius);
gl.glTexCoord2d(0, 0);
gl.glVertex3d(p1.x(), p1.y(), p1.z());
gl.glTexCoord2d(1, 0);
gl.glVertex3d(p2.x(), p2.y(), p2.z());
gl.glTexCoord2d(1, 1);
gl.glVertex3d(p3.x(), p3.y(), p3.z());
gl.glTexCoord2d(0, 1);
gl.glVertex3d(p4.x(), p4.y(), p4.z());
}
}
gl.glEnd();
gl.glDisable(GL_TEXTURE_2D);
}
Vector getPoints(double phi, double theta, double radius) {
double x = radius * cos(theta) * sin(phi);
double y = radius * sin(theta) * sin(phi);
double z = radius * cos(phi);
return new Vector(x, y, z);
}
}
You could just map latitude and longitude directly to the texture co-ordinates.
for (double theta = 0; theta < 2 * PI; theta += stack) {
for (double phi = 0; phi < 2 * PI; phi += slice) {
Just scale theta and phi to be between 0 and 1.
double s0 = theta / (2 * PI);
double s1 = (theta + stack) / (2 * PI);
double t0 = phi / (2 * PI);
double t1 = (phi + slice) / (2 * PI);
And use s0,s1,t0,t1 in place of 0 and 1 in your texCoord() calls.