Hello!
I am trying to draw a semisphere using verticies, but for some reason I get weird artifacts, when two or more “rings” are drawn behind each other. I already tried to use illumination (with a point light at 0,0,0 as well as emmissive material) but that didn’t help either.
Can someone please help me?
would like to see what you see?
your code:
test:
// for (a=0; a < TWO_PI+da; a += da) {
for (a=0; a < TWO_PI; a += da) {
still that dot in the middle??
For me the dot in the middle is still visible, but that is not that important compared to the dark “shadow” appearing all over the surface
It seems like I jusf fixed the middle dot like this
//for (b=0; b < HALF_PI; b += db) {
for (b=0; b < HALF_PI-db; b += db) {
very good,
now i would recommend
not construct the shape at runtime ( inside draw ),
and play with stroke for visibility ( pls, change back )
add instead for test/inspect not use the auto rotate,
here i try my PTZ
// https://discourse.processing.org/t/semicircle-drawing-producing-artifacts/8444
PShape myshape;
void setup() {
size(600, 600, P3D);
make_myshape(100, 30, 30);
info_print();
}
void draw() {
background(0, 0, 80);
PTZ();
}
void make_myshape(float radius, float slicesA, float slicesB) {
float a, b, x, y, z, da, db;
da = TWO_PI / slicesA;
db = HALF_PI / slicesB;
myshape = createShape();
myshape.beginShape(QUAD_STRIP);
myshape.fill(0, 255, 0, 127);
// myshape.noStroke();
myshape.stroke(0, 255, 0, 127); // test visibility
for (b=0; b < HALF_PI-db; b += db) {
for (a=0; a < TWO_PI; a += da) {
x = cos(a) * cos(b) * radius;
y = sin(a) * cos(b) * radius;
z = sin(b) * radius;
myshape.vertex(x, y, z);
x = cos(a) * cos(b+db) * radius;
y = sin(a) * cos(b+db) * radius;
z = sin(b+db) * radius;
myshape.vertex(x, y, z);
}
}
myshape.endShape();
}
//______________________________________
void draw_object() { //_________________called by / from inside PTZ
shape(myshape, 0, 0);
}
//_____________________________________ PTZ tab
int mode = 0;
float Zmag = 2;
int Zaxis=-10;
float Xmag, Ymag = 0;
float newXmag, newYmag = 0;
int newZmag = 0;
int zoomf = 3;
float newxpos, newypos = 0; // for PAN
float xposd, yposd = 0; // for PAN
//_________________________________________________________________ ROTATE / TILDE and MOVE / PAN
void mousePressed() {
if (mouseButton == LEFT) {
mode=1;
} // ORBIT
else if (mouseButton == RIGHT) {
mode=2;
} // PAN
// else if (mouseButton == CENTER) { mode=3; } // zoom mouse wheel works same , presssed or not
}
//_________________________________________________________________ mouse PT end
void mouseReleased() {
mode = 0;
}
//_________________________________________________________________ mouseWheel ZOOM
void mouseWheel(MouseEvent event) {
int newZmag = event.getCount(); // +- 1
//if (Zmag > 10) { Zmag += newZmag * 5; } else { Zmag += newZmag; }// from 1 to 11 go in step 1 else in step 5
Zmag += newZmag*0.3;
//println("Zmag: "+nf(Zmag, 1, 2));
}
void keyPressed() {
if ( keyCode == UP ) Ymag -= 0.1 ;
if ( keyCode == DOWN ) Ymag += 0.1 ;
if ( keyCode == RIGHT) Xmag -= 0.1 ;
if ( keyCode == LEFT ) Xmag += 0.1 ;
if ( keyCode == 16 ) Zmag -= 0.5 ;
if ( keyCode == 11 ) Zmag += 0.5 ;
//println("key: "+key); println("keyCode: "+keyCode);
}
//_________________________________________________________________ Pan Tilde Zoom
void PTZ() {
pushMatrix();
translate(width/2, height/2, Zaxis);
// get new mouse operation
if ( mode == 2 ) { // PAN ( right mouse button pressed)
xposd = (mouseX-float(width/2));
yposd = (mouseY-float(height/2));
}
newxpos = xposd;// xposd=0;
newypos = yposd;// yposd = 0;
translate(newxpos, newypos, 0); // move object
if ( mode == 1 ) { // ORBIT ( left mouse button pressed)
newXmag = mouseX/float(width) * TWO_PI;
newYmag = mouseY/float(height) * TWO_PI;
float diff = Xmag-newXmag;
if (abs(diff) > 0.01) Xmag -= diff/4.0;
diff = Ymag-newYmag;
if (abs(diff) > 0.01) Ymag -= diff/4.0;
}
rotateX(-Ymag);
rotateY(-Xmag);
scale(Zmag);
draw_object(); // THE OBJECT see main tab
popMatrix();
}
//_______________________________________________ SETUP PRINT INFO
void info_print() {
println("PTZ info:");
println("key UP DOWN RIGHT LEFT -> rotate // key PAGE UP DOWN -> zoom");
println("mouse LEFT press drag up down right left -> rotate // mouse RIGHT press -> move // mouse WHEEL turn -> zoom");
}
Thanks for your advice, but my problem still persists where a light area appears where the bottom is visible through the top.
but it doesn’t appear to be happening when it is a highet level in the background Image
without light area, for reference
I’m wondering; is it possible to probhibit a shape to be visible through itself causing those areas to get darker…?
?? you started with transparency
fill(0, 255, 0, 127);
did you try without?
or is it that default inside / outside rendering look?
i have no idea where it comes from and how to change
when i wanted a different inside and outside color
i draw it 2 times, the second / with a other color / some pix bigger.
or you go the next step using texture.
Yes, I want transparency so that i can see some other objects behind that, but i don’t want the back of the hemisphere to affect the transparency -> everything should be tinted the same way at any rotation…
It seems that you don’t want a transparent sphere – what you want is to make an opaque image of a sphere, then make that flat image transparent. For example, you could do this by drawing the image opaquely onto a PGraphics, then setting transparency and drawing the image onto your main sketch canvas.
There are also various depth hints like that you might try playing around with:
hint(DISABLE_DEPTH_MASK)
hint(ENABLE_DEPTH_MASK)
hint(ENABLE_DEPTH_TEST)
hint(DISABLE_DEPTH_TEST)