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Draw triangle iphone


Draw triangle iphone

By : user3862078
Date : November 22 2020, 07:01 PM
I hope this helps you . You should take a look at QuartzDemo from Apple Documentation, which have a lot of examples of drawings.
Using this demo, you can change de star (6 edges) to a triangle (3 edges) in the Polygon demo. Just change the number of incrementation in the loop of QuartzPolygons.m, just bellow the comment "// Add a star to the current path". For example, here is the code for an equilateral triangle :
code :


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Draw a triangle using mouse drag (how can I move the previous drawn triangle using mouse drag)

Draw a triangle using mouse drag (how can I move the previous drawn triangle using mouse drag)


By : Ashley Guevara Nord
Date : March 29 2020, 07:55 AM
this one helps. when you start to drag you have to detect if your current mouse location is on one of the existing Polygons, also mark the starting location
When it is you dont add a new polygon, but you add the amount moved to the different points of the existing polygon and repaint
Draw image in triangle region iphone

Draw image in triangle region iphone


By : abdalrahman
Date : March 29 2020, 07:55 AM
To fix this issue After adding the lines into the context call CGContextClip then draw your image (CGContextDrawImage). Your image will be clipped by the path. You can then use the same path to draw the triangle as lines too, if you like.
You'll probably find that your image is upside down, so you may need to apply a transform before drawing it - something like:
How many draw calls is necessary to draw a triangle fan in OpenGL ES?

How many draw calls is necessary to draw a triangle fan in OpenGL ES?


By : Raphael Rudu
Date : March 29 2020, 07:55 AM
will be helpful for those in need OpenGL has a GL_TRIANGLE_FAN primitive type. So you can draw a triangle fan with a single draw call:
code :
glDrawArrays(GL_TRIANGLE_FAN, ...);
glDrawElements(GL_TRIANGLE_FAN, ...);
0, 1, 2
0, 2, 3
0, 3, 4
...
0, n - 2, n - 1
How to draw a triangle?

How to draw a triangle?


By : Yulia Ohrymovych
Date : March 29 2020, 07:55 AM
it should still fix some issue The last element of the array must be same as first (to close the figure)
code :
Dim trianglePoints As PointF() =
    {
        New PointF(p.Width / 2.0F, CSng(Me.Height) - (p.Width / 2.0F)),
        New PointF(CSng(Me.Width) / 2.0F, p.Width / 2F),
        New PointF(CSng(Me.Width) - (p.Width / 2.0F), CSng(Me.Height) - (p.Width / 2.0F)),
        New PointF(p.Width / 2.0F, CSng(Me.Height) - (p.Width / 2.0F))
    }
Is passing just the length of the sides of a triangle, sufficient to draw a triangle in WebGL?

Is passing just the length of the sides of a triangle, sufficient to draw a triangle in WebGL?


By : user3379855
Date : March 29 2020, 07:55 AM
this one helps. WebGL only cares that you set gl_Position to clip space values. It doesn't care how you do it. It's up to you to decide how to do that. Inside the vertex shader, at least in WebGL1, things are stateless. Meaning when you draw a triangle your vertex shader will be called 3 times. It needs to set gl_Position to 3 different values in clipspace with no state between calls. So given 100 three times, how would you compute a different value each time your vertex shader is called?
Just imagine it in JavaScript
code :
const gl_Position1 = vertexShader(100);
const gl_Position2 = vertexShader(100);
const gl_Position3 = vertexShader(100);
function vertexShader(v) {
  const angle = v / 3 * Math.PI * 2;
  return [Math.cos(angle), Math.sin(angle), 0, 1];
}

const gl_Position1 = vertexShader(0);
const gl_Position2 = vertexShader(1);
const gl_Position3 = vertexShader(2);
const gl = document.querySelector('canvas').getContext('webgl');

const vs = `
attribute float v;

#define PI radians(180.0)

void main() {
  float angle = v / 3.0 * PI * 2.0;
  gl_Position = vec4(cos(angle), sin(angle), 0, 1);
}
`;

const fs = `
precision mediump float;
void main() {
  gl_FragColor = vec4(1, 0, 0, 1);
}
`;

const program = twgl.createProgram(gl, [vs, fs]);
const vLocation = gl.getAttribLocation(program, 'v');

const buf = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, buf);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([0, 1, 2]), gl.STATIC_DRAW);

gl.enableVertexAttribArray(vLocation);
gl.vertexAttribPointer(vLocation, 1, gl.FLOAT, false, 0, 0);

gl.useProgram(program);
gl.drawArrays(gl.TRIANGLES, 0, 3);
canvas { border: 1px solid black; }
<script src="https://twgljs.org/dist/4.x/twgl.min.js"></script>
<canvas></canvas>
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