I'm trying to learn how to use OpenGL in a 2D application by using OpenTK and have read that using the inbuilt calls glMatrixMode are not modern. I want to use top left origin and pixel co-ordinates in my shader inputs and assumed I could define a matrix to do these translations.
I am trying to do this using my own matrix using the OpenTK matrix clases. However I think I have made a mistake in setting up the projection matrix and want to verify what I should be doing:-
TranslationMatrix = Matrix4.Identity * Matrix4.CreateScale(1, -1, 1);
TranslationMatrix = TranslationMatrix * Matrix4.CreateOrthographicOffCenter(0, bounds.Width, 0, bounds.Height, -1, 1);
var TranslatedPoint = TranslationMatrix * new Vector4(new Vector3(1024, 768, 0), 1); // bounds = {0, 0, 1024, 768 }
This results in x.Xyz == { 2, -2, 0 }. I thought that the x and y co-ordinates used in gl_position in the vertex shader should range from -1 to 1.
I guess I've got a major misunderstanding somewhere, what should I be looking at?
OpenTK stores the matrices in transposed form. This means you have to write everything in reversed order.
var TranslationMatrix = Matrix4.CreateOrthographicOffCenter(0, bounds.Width, 0, bounds.Height, -1, 1);
TranslationMatrix = TranslationMatrix * Matrix4.CreateScale(1, -1, 1);
var TranslatedPoint = new Vector4(1024, 768, 0, 1) * TranslationMatrix;
The result should now be [1, -1, 0, 1].
Related
What is the way to set and get position of imported STL file. I'm looking for a solution to set position x,y,z to imported STL file like is possible for example to Joint.
Normally things are moved in eyeshot by a transformation matrix. This matrix consists of a rotation matrix 3 x 3, a location 1 x 3, and skew/stretch 4 x 1. All together this makes a 4 x 4 transformation matrix.
an imported stl actually contains lots of locations. But all you need to do is grab one of these. below I have just grabbed the min point of the bounding box.
Then to get to a place create an identity transformation matrix to ensure the rotation and skew are Zero. Now insert your location into the location part of the matrix. The transformBy function will now move every point of the stl to a new location.
to move between points you need the vector difference between the points.
Mesh myMesh = Mesh.CreateBox(10, 10, 10);
//Mesh myMesh = new Mesh();
Point3D getLocation = myMesh.BoxMin;
Point3D setLocation = new Point3D(20, -10, 0);
Point3D moveVector = setLocation - getLocation;
Transformation goPlaces = new Transformation(1);
goPlaces[0, 3] = moveVector.X;
goPlaces[1, 3] = moveVector.Y;
goPlaces[2, 3] = moveVector.Z;
//Transformation goPlaces = new Transformation(
// new double[,]
// {
// { 1, 0, 0, 20 },
// { 0, 1, 0,-10 },
// { 0, 0, 1, 0 },
// { 0, 0, 0, 1 }
// }
//);
Transformation goBack = (Transformation)goPlaces.Clone();
goBack.Invert();
myMesh.TransformBy(goPlaces);
myMesh.TransformBy(goBack);
Cheers!
I'm trying to make a rendering library for monogame and I'm currently working on drawing 2D polygons. However, The positions don't make any sense. Somehow, drawing them at (0, 0, 0), (100. 0, 0), (0, 100, 0), and (100, 100, 0) doesn't reach the top-left coordinate (0, 0). How do I fix this?
My Code:
BasicEffect basicEffect = new BasicEffect(GraphicsDevice);
VertexPositionColor[] vert = new VertexPositionColor[4];
vert[0].Position = new Vector3(0, 0, 0);
vert[1].Position = new Vector3(100, 0, 0);
vert[2].Position = new Vector3(0, 100, 0);
vert[3].Position = new Vector3(100, 100, 0);
short[] ind = new short[6];
ind[0] = 0;
ind[1] = 2;
ind[2] = 1;
ind[3] = 1;
ind[4] = 2;
ind[5] = 3;
foreach (EffectPass effectPass in basicEffect.CurrentTechnique.Passes)
{
effectPass.Apply();
GraphicsDevice.DrawUserIndexedPrimitives<VertexPositionColor>(
PrimitiveType.TriangleList, vert, 0, vert.Length, ind, 0, ind.Length / 3);
}
RESULT: https://imgur.com/GkyqmlY
MonoGame uses a different origin for 2D and 3D coordinate systems. In 2D, (0, 0) is top-left corner, and Y increases toward the bottom of the screen. In 3D, (0,0,0) is the center of the screen, and the coordinate grid works very much like it does in mathematics - think 4 quadrants in math, if you "flatten" the z-axis.
You're drawing in Quadrant I. If you want the drawing to be based on top-left corner, you need to translate your vertices by -1/2 your viewport width and +1/2 your viewport height.
I need help from any C# and or OpenCV experts in making my circle detection script more accurate.
In OpenCV circle detection is accomplished by something called HoughCircles algorithm or framework.
http://docs.opencv.org/doc/tutorials/imgproc/imgtrans/hough_circle/hough_circle.html
I am using a C# wrapper of OpenCV (for Unity)OpenCVforUnity HughCircles
which in turn is directly based on the official java wrapper of OpenCV.
My circle detection code is as follows (without the OpenCv dependencies of course)
I've also attached 2 images so you can see the results.
What changes are needed to improve the results? I've also included the original 2 images for reference.
using UnityEngine;
using System.Collections;
using System;
using OpenCVForUnity;
public class HoughCircleSample : MonoBehaviour{
Point pt;
// Use this for initialization
void Start ()
{
Texture2D imgTexture = Resources.Load ("balls2_bw") as Texture2D;
Mat imgMat = new Mat (imgTexture.height, imgTexture.width, CvType.CV_8UC3);
Utils.texture2DToMat (imgTexture, imgMat);
//Debug.Log ("imgMat dst ToString " + imgMat.ToString ());
Mat grayMat = new Mat ();
Imgproc.cvtColor (imgMat, grayMat, Imgproc.COLOR_RGB2GRAY);
Imgproc.Canny (grayMat, grayMat, 50, 200);
Mat circles = new Mat();
int minRadius = 0;
int maxRadius = 0;
// Apply the Hough Transform to find the circles
Imgproc.HoughCircles(grayMat, circles, Imgproc.CV_HOUGH_GRADIENT, 3, grayMat.rows() / 8, 200, 100, minRadius, maxRadius);
Debug.Log ("circles toString " + circles.ToString ());
Debug.Log ("circles dump" + circles.dump ());
if (circles.cols() > 0)
for (int x = 0; x < Math.Min(circles.cols(), 10); x++)
{
double[] vCircle = circles.get(0, x);
if (vCircle == null)
break;
pt = new Point(Math.Round(vCircle[0]), Math.Round(vCircle[1]));
int radius = (int)Math.Round(vCircle[2]);
// draw the found circle
Core.circle(imgMat, pt, radius, new Scalar(255, 0, 0), 1);
}
Texture2D texture = new Texture2D (imgMat.cols (), imgMat.rows (), TextureFormat.RGBA32, false);
Utils.matToTexture2D (imgMat, texture);
gameObject.GetComponent<Renderer> ().material.mainTexture = texture;
}
}
This code is in C++, but you can easily convert to C#.
I needed to change the param2 of HoughCircle to 200, resulting in:
HoughCircles(grayMat, circles, CV_HOUGH_GRADIENT, 3, grayMat.rows / 8, 200, 200, 0, 0);
which is
the accumulator threshold for the circle centers at the detection stage. The smaller it is, the more false circles may be detected. Circles, corresponding to the larger accumulator values, will be returned first.
You also should't feed HoughCircles with a "Canny-ed" image, since will already take care of this. Use the grayMat without Canny edge detection step applied.
Results are shown below. The second one is more tricky, because of the light conditions.
Here is the whole code. Again, it's C++, but may be useful as a reference.
#include <opencv2/opencv.hpp>
using namespace cv;
int main(){
Mat3b src = imread("path_to_image");
Mat1b src_gray;
cvtColor(src, src_gray, CV_BGR2GRAY);
vector<Vec3f> circles;
HoughCircles(src_gray, circles, CV_HOUGH_GRADIENT, 3, src_gray.rows / 8, 200, 200, 0, 0);
/// Draw the circles detected
for (size_t i = 0; i < circles.size(); i++)
{
Point center(cvRound(circles[i][0]), cvRound(circles[i][1]));
int radius = cvRound(circles[i][2]);
// circle center
circle(src, center, 3, Scalar(0, 255, 0), -1, 8, 0);
// circle outline
circle(src, center, radius, Scalar(0, 0, 255), 3, 8, 0);
}
imshow("src", src);
waitKey();
return 0;
}
In the fourth parameter you have set a 3, but most of your images have a ratio close to 1, this could be a probable improvement, also you have to try another set of values in the parameters 6 and 7, because this values depend on the contours extracted by a canny edge detector, I hope this could help you.
I'm getting much closer now with 2 overlapping circles for each ball object. If I can correct for this it is basically solved.
Imgproc.Canny (grayMat, grayMat, 500, 200);
Mat circles = new Mat();
int minRadius =50;
int maxRadius = 200;
Imgproc.HoughCircles(grayMat, circles, Imgproc.CV_HOUGH_GRADIENT, 1, grayMat.rows() / 4, 1000, 1, minRadius, maxRadius);![solution3][1]
I'm trying to calculate Gradient Magnitude and Orientation of a garyscale Image using OpenCvSharp. The problem is that "Pow" function seems to not be the right for the IplImage.
I also want to know how can I calculate tan-1 (or arctan) of featureImage.
Thank you
using (IplImage cvImage = new IplImage("grayImage.png", LoadMode.AnyDepth |
LoadMode.GrayScale))
using (IplImage dstXImage = new IplImage(cvImage.Size, cvImage.Depth, cvImage.NChannels))
using (IplImage dstYImage = new IplImage(cvImage.Size, cvImage.Depth, cvImage.NChannels))
{
float[] data = { 0, -1, -1, 2 };
CvMat kernel = new CvMat(2, 2, MatrixType.F32C1, data);
Cv.Sobel(cvImage, dstXImage, 1, 0, ApertureSize.Size1);
Cv.Sobel(cvImage, dstYImage, 0, 1, ApertureSize.Size1);
Cv.Normalize(dstXImage, dstXImage, 1.0, 0, NormType.L1);
Cv.Filter2D(cvImage, dstXImage, kernel, new CvPoint(0, 0));
Cv.Normalize(dstYImage, dstYImage, 1.0, 0, NormType.L1);
Cv.Filter2D(cvImage, dstYImage, kernel, new CvPoint(0, 0));
// to calculate gradient magnitude, sqrt[(dy)power 2 + (dx)power 2]
dstXImage.Mul(dstXImage, dstXImage);
dstYImage.Mul(dstYImage, dstYImage);
IplImage dstXYImage = new IplImage(cvImage.Size, cvImage.Depth, cvImage.NChannels);
dstXImage.Add(dstYImage, dstXYImage);
dstXYImage.Pow(dstXYImage, 1/2); //this line not working,output image is black page
// to calculate gradient orientation, arctan(dy/dx)
IplImage thetaImage = new IplImage(cvImage.Size, cvImage.Depth, cvImage.NChannels);
dstYImage.Div(dstXImage, thetaImage); //afterwards need help to calculate arctan
using (new CvWindow("SrcImage", cvImage))
using (new CvWindow("DstXImage", dstXImage))
using (new CvWindow("DstYImage", dstYImage))
using (new CvWindow("DstXYImage", dstXYImage))
using (new CvWindow("thetaImage", thetaImage))
{
Cv.WaitKey(0);
}
You can use the "cartToPolar" function for your purpose.
This function calculates the magnitude and angle of 2D vectors.
magnitude(I)= sqrt(x(I)^2+y(I)^2),
angle(I)= atan2(y(I), x(I))[ *180 / pi ]
For example:
IplImage dstXYImage;
IplImage thetaImage;
CartToPolar(dstXImage, dstYImage, dstXYImage, thetaImage, true);
I have massive Problems figuring out how to set up a dynamic VertexBuffer and IndexBuffer using SharpDX.
I have to generate Triangles where ever the User presses on the Screen.
I think i have to set up a transformation function that converts my screen coordinates to projection coordinates.
But i dont ever come this far...
I want to set up a Buffer with space for 10000 Vertices.
layout = new InputLayout(d3dDevice, vertexShaderByteCode, new[]
{
new SharpDX.Direct3D11.InputElement("POSITION", 0, Format.R32G32B32A32_Float, 0, 0),
new SharpDX.Direct3D11.InputElement("COLOR", 0, Format.R32G32B32A32_Float, 16, 0)
});
vb = Buffer.Create(d3dDevice, BindFlags.VertexBuffer, stream, 10000, ResourceUsage.Dynamic, CpuAccessFlags.Write);
vertexBufferBinding = new VertexBufferBinding(vb, Utilities.SizeOf<Vector4>() * 2, 0);
That Buffer i want to update every time i have to add new triangles using:
d3dDevice.ImmediateContext.UpdateSubresource(updateVB, vb);
updateVB are the new Triangles to be added.
Rendering works the following way:
// Prepare matrices
var view = Matrix.LookAtLH(new Vector3(0, 0, -5), new Vector3(0, 0, 0), Vector3.UnitY);
var proj = Matrix.PerspectiveFovLH((float)Math.PI / 4.0f, width / (float)height, 0.1f, 100.0f);
var viewProj = Matrix.Multiply(view, proj);
// Set targets (This is mandatory in the loop)
d3dContext.OutputMerger.SetTargets(render.DepthStencilView, render.RenderTargetView);
// Clear the views
d3dContext.ClearDepthStencilView(render.DepthStencilView, DepthStencilClearFlags.Depth, 1.0f, 0);
d3dContext.ClearRenderTargetView(render.RenderTargetView, Colors.Black);
// Calculate WorldViewProj
var worldViewProj = Matrix.Scaling(1f) * viewProj;
worldViewProj.Transpose();
// Setup the pipeline
d3dContext.InputAssembler.SetVertexBuffers(0, vertexBufferBinding);
d3dContext.InputAssembler.InputLayout = layout;
d3dContext.InputAssembler.PrimitiveTopology = PrimitiveTopology.TriangleList;
d3dContext.VertexShader.Set(vertexShader);
d3dContext.PixelShader.Set(pixelShader);
d3dContext.Draw(vertexCount, 0);
I am new to DirectX and the DirectX9 tutorials on the web don't help me very good with DirectX11.1.
Thanks
vb = Buffer.Create(d3dDevice, BindFlags.VertexBuffer, stream, 10000, ResourceUsage.Dynamic, CpuAccessFlags.Write);
Is wrong, since you want 10000 vertices, but allocate 10000 bytes, so should be:
10000 * sizeof(Vector4) * 2
According to your input layout.
Also to write into your buffer, you should look at context.MapSubresource instead.