[SOLVED - See answer in bottom]
I'm trying to draw a cube with perspective, using OpenGL ES 2.0 on iOS (iPhone), but it's appearing as a rectangular shape.
From what I've gathered searching the web it seems to be related to the viewport / projection matrix, but I can't seem to put the finger on the actual cause.
If I set the viewport to a square measure (width == height) it draws perfectly well (a cube), but if I set it correctly (width = screen_width, height = screen_height) then the cube is drawn as a rectangular shape.
Should setting the Projection matrix accordingly with the Viewport make the cube stay a cube?!
My code (please let me know if more info is needed):
Render method:
// viewportSize is SCREEN_WIDTH and SCREEN_HEIGHT
// viewportLowerLeft is 0.0 and 0.0
ivec2 size = this->viewportSize;
ivec2 lowerLeft = this->viewportLowerLeft;
glViewport(lowerLeft.x, lowerLeft.y, size.x, size.y); // if I put size.x, size.x it draws well
mat4 projectionMatrix = mat4::FOVFrustum(45.0, 0.1, 100.0, size.x / size.y);
glUniformMatrix4fv(uniforms.Projection, 1, 0, projectionMatrix.Pointer());
Matrix operations:
static Matrix4<T> Frustum(T left, T right, T bottom, T top, T near, T far)
{
T a = 2 * near / (right - left);
T b = 2 * near / (top - bottom);
T c = (right + left) / (right - left);
T d = (top + bottom) / (top - bottom);
T e = - (far + near) / (far - near);
T f = -2 * far * near / (far - near);
Matrix4 m;
m.x.x = a; m.x.y = 0; m.x.z = 0; m.x.w = 0;
m.y.x = 0; m.y.y = b; m.y.z = 0; m.y.w = 0;
m.z.x = c; m.z.y = d; m.z.z = e; m.z.w = -1;
m.w.x = 0; m.w.y = 0; m.w.z = f; m.w.w = 1;
return m;
}
static Matrix4<T> FOVFrustum(T fieldOfView, T near, T far, T aspectRatio)
{
T size = near * tanf(DEGREES_TO_RADIANS(fieldOfView) / 2.0);
return Frustum(-size, size, -size / aspectRatio, size / aspectRatio, near, far);
}
If you haven't figured this out already, change:
return Frustum(-size, size, -size / aspectRatio, size / aspectRatio, near, far);
to
return Frustum(-size / aspectRatio, size / aspectRatio, -size, size,, near, far);
and it should draw correctly.
(or simply change the ratio from size.x/size.y to size.y/size.x)
Ok I found out the problem, size.x and size.y are int, so the division returns an int.
1.0 * size.x / size.y
Solves the problem.
facepalm
Related
I have a video stream coming from a 180 degree fisheye camera. I want to do some image-processing to convert the fisheye view into a normal view.
After some research and lots of read articles I found this paper.
They describe an algorithm (and some formulas) to solve this problem.
I used tried to implement this method in a Matlab. Unfortunately it doesn't work, and I failed to make it work. The "corrected" image looks exactly like the original photograph and there's no any removal of distortion and secondly I am just receiving top left side of the image, not the complete image but changing the value of 'K' to 1.9 gives mw the whole image, but its exactly the same image.
Input image:
Result:
When the value of K is 1.15 as mentioned in the article
When the value of K is 1.9
Here is my code:
image = imread('image2.png');
[Cx, Cy, channel] = size(image);
k = 1.5;
f = (Cx * Cy)/3;
opw = fix(f * tan(asin(sin(atan((Cx/2)/f)) * k)));
oph = fix(f * tan(asin(sin(atan((Cy/2)/f)) * k)));
image_new = zeros(opw, oph,channel);
for i = 1: opw
for j = 1: oph
[theta,rho] = cart2pol(i,j);
R = f * tan(asin(sin(atan(rho/f)) * k));
r = f * tan(asin(sin(atan(R/f))/k));
X = ceil(r * cos(theta));
Y = ceil(r * sin(theta));
for k = 1: 3
image_new(i,j,k) = image(X,Y,k);
end
end
end
image_new = uint8(image_new);
warning('off', 'Images:initSize:adjustingMag');
imshow(image_new);
This is what solved my problem.
input:
strength as floating point >= 0. 0 = no change, high numbers equal stronger correction.
zoom as floating point >= 1. (1 = no change in zoom)
algorithm:
set halfWidth = imageWidth / 2
set halfHeight = imageHeight / 2
if strength = 0 then strength = 0.00001
set correctionRadius = squareroot(imageWidth ^ 2 + imageHeight ^ 2) / strength
for each pixel (x,y) in destinationImage
set newX = x - halfWidth
set newY = y - halfHeight
set distance = squareroot(newX ^ 2 + newY ^ 2)
set r = distance / correctionRadius
if r = 0 then
set theta = 1
else
set theta = arctangent(r) / r
set sourceX = halfWidth + theta * newX * zoom
set sourceY = halfHeight + theta * newY * zoom
set color of pixel (x, y) to color of source image pixel at (sourceX, sourceY)
I am following the quaternion tutorial: http://www.raywenderlich.com/12667/how-to-rotate-a-3d-object-using-touches-with-opengl and am trying to rotate a globe to some XYZ location. I have an initial quaternion and generate a random XYZ location on the surface of the globe. I pass that XYZ location into the following function. The idea was to generate a lookAt vector with GLKMatrix4MakeLookAt and define the end Quaternion for the slerp step from the lookAt matrix.
- (void)rotateToLocationX:(float)x andY:(float)y andZ:(float)z {
// Turn on the interpolation for smooth rotation
_slerping = YES; // Begin auto rotating to this location
_slerpCur = 0;
_slerpMax = 1.0;
_slerpStart = _quat;
// The eye location is defined by the look at location multiplied by this modifier
float modifier = 1.0;
// Create a look at vector for which we will create a GLK4Matrix from
float xEye = x;
float yEye = y;
float zEye = z;
//NSLog(#"%f %f %f %f %f %f",xEye, yEye, zEye, x, y, z);
_currentSatelliteLocation = GLKMatrix4MakeLookAt(xEye, yEye, zEye, 0, 0, 0, 0, 1, 0);
_currentSatelliteLocation = GLKMatrix4Multiply(_currentSatelliteLocation,self.effect.transform.modelviewMatrix);
// Turn our 4x4 matrix into a quat and use it to mark the end point of our interpolation
//_currentSatelliteLocation = GLKMatrix4Translate(_currentSatelliteLocation, 0.0f, 0.0f, GLOBAL_EARTH_Z_LOCATION);
_slerpEnd = GLKQuaternionMakeWithMatrix4(_currentSatelliteLocation);
// Print info on the quat
GLKVector3 vec = GLKQuaternionAxis(_slerpEnd);
float angle = GLKQuaternionAngle(_slerpEnd);
//NSLog(#"%f %f %f %f",vec.x,vec.y,vec.z,angle);
NSLog(#"Quat end:");
[self printMatrix:_currentSatelliteLocation];
//[self printMatrix:self.effect.transform.modelviewMatrix];
}
The interpolation works, I get a smooth rotation, however the ending location is never the XYZ I input - I know this because my globe is a sphere and I am calculating XYZ from Lat Lon. I want to look directly down the 'lookAt' vector toward the center of the earth from that lat/lon location on the surface of the globe after the rotation. I think it may have something to do with the up vector but I've tried everything that made sense.
What am I doing wrong - How can I define a final quaternion that when I finish rotating, looks down a vector to the XYZ on the surface of the globe? Thanks!
Is the following your meaning:
Your globe center is (0, 0, 0), radius is R, the start position is (0, 0, R), your final position is (0, R, 0), so rotate the globe 90 degrees around X-asix?
If so, just set lookat function eye position to your final position, the look at parameters to the globe center.
m_target.x = 0.0f;
m_target.y = 0.0f;
m_target.z = 1.0f;
m_right.x = 1.0f;
m_right.y = 0.0f;
m_right.z = 0.0f;
m_up.x = 0.0f;
m_up.y = 1.0f;
m_up.z = 0.0f;
void CCamera::RotateX( float amount )
{
Point3D target = m_target;
Point3D up = m_up;
amount = amount / 180 * PI;
m_target.x = (cos(PI / 2 - amount) * up.x) + (cos(amount) * target.x);
m_target.y = (cos(PI / 2 - amount) * up.y) + (cos(amount) * target.y);
m_target.z = (cos(PI / 2 - amount) * up.z) + (cos(amount) * target.z);
m_up.x = (cos(amount) * up.x) + (cos(PI / 2 + amount) * target.x);
m_up.y = (cos(amount) * up.y) + (cos(PI / 2 + amount) * target.y);
m_up.z = (cos(amount) * up.z) + (cos(PI / 2 + amount) * target.z);
Normalize(m_target);
Normalize(m_up);
}
void CCamera::RotateY( float amount )
{
Point3D target = m_target;
Point3D right = m_right;
amount = amount / 180 * PI;
m_target.x = (cos(PI / 2 + amount) * right.x) + (cos(amount) * target.x);
m_target.y = (cos(PI / 2 + amount) * right.y) + (cos(amount) * target.y);
m_target.z = (cos(PI / 2 + amount) * right.z) + (cos(amount) * target.z);
m_right.x = (cos(amount) * right.x) + (cos(PI / 2 - amount) * target.x);
m_right.y = (cos(amount) * right.y) + (cos(PI / 2 - amount) * target.y);
m_right.z = (cos(amount) * right.z) + (cos(PI / 2 - amount) * target.z);
Normalize(m_target);
Normalize(m_right);
}
void CCamera::RotateZ( float amount )
{
Point3D right = m_right;
Point3D up = m_up;
amount = amount / 180 * PI;
m_up.x = (cos(amount) * up.x) + (cos(PI / 2 - amount) * right.x);
m_up.y = (cos(amount) * up.y) + (cos(PI / 2 - amount) * right.y);
m_up.z = (cos(amount) * up.z) + (cos(PI / 2 - amount) * right.z);
m_right.x = (cos(PI / 2 + amount) * up.x) + (cos(amount) * right.x);
m_right.y = (cos(PI / 2 + amount) * up.y) + (cos(amount) * right.y);
m_right.z = (cos(PI / 2 + amount) * up.z) + (cos(amount) * right.z);
Normalize(m_right);
Normalize(m_up);
}
void CCamera::Normalize( Point3D &p )
{
float length = sqrt(p.x * p.x + p.y * p.y + p.z * p.z);
if (1 == length || 0 == length)
{
return;
}
float scaleFactor = 1.0 / length;
p.x *= scaleFactor;
p.y *= scaleFactor;
p.z *= scaleFactor;
}
The answer to this question is a combination of the following rotateTo function and a change to the code from Ray's tutorial at ( http://www.raywenderlich.com/12667/how-to-rotate-a-3d-object-using-touches-with-opengl ). As one of the comments on that article says there is an arbitrary factor of 2.0 being multiplied in GLKQuaternion Q_rot = GLKQuaternionMakeWithAngleAndVector3Axis(angle * 2.0, axis);. Remove that "2" and use the following function to create the _slerpEnd - after that the globe will rotate smoothly to XYZ specified.
// Rotate the globe using Slerp interpolation to an XYZ coordinate
- (void)rotateToLocationX:(float)x andY:(float)y andZ:(float)z {
// Turn on the interpolation for smooth rotation
_slerping = YES; // Begin auto rotating to this location
_slerpCur = 0;
_slerpMax = 1.0;
_slerpStart = _quat;
// Create a look at vector for which we will create a GLK4Matrix from
float xEye = x;
float yEye = y;
float zEye = z;
_currentSatelliteLocation = GLKMatrix4MakeLookAt(xEye, yEye, zEye, 0, 0, 0, 0, 1, 0);
// Turn our 4x4 matrix into a quat and use it to mark the end point of our interpolation
_slerpEnd = GLKQuaternionMakeWithMatrix4(_currentSatelliteLocation);
}
I have reached up to image shown in the snapshot.
But still its Y is at bottom only and I am not able to set the X properly overlapped.
Images at Y can be up and down but cannot have the same Y as of pervious Image.
Image at X have to be overlapped to previous but can not have distance between any of Image.
I was able to set Y but still It should be in the middle of screen and not at bottom and not able to set X.
This is the code I am using
CGFloat randomX = (arc4random()%100) *1.1;
CGFloat randomY = (arc4random()%100) *.40;
UICollectionViewLayoutAttributes* attributes = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:path];
NSLog(#"prevnode : %#",NSStringFromCGPoint(prevNodeCenter));
attributes.size = CGSizeMake(ITEM_SIZE, ITEM_SIZE);
attributes.center = CGPointMake(_center.x + _radius + randomX * cosf(2 * path.item * M_PI / _cellCount) ,
_center.y + _radius + randomY);
NSLog(#"randomX : %f randomY : %f",randomX,randomY);
NSLog(#"attrib center x : %f",attributes.center.x);
/*
if(attributes.center.x <= prevNodeCenter.x )
{
attributes.center = CGPointMake(prevNodeCenter.x+_radius+cosf(2 * path.item * M_PI / _cellCount), attributes.center.y);
}
if(attributes.center.x >= prevNodeCenter.x+_radius)
{
NSLog(#"its far");
}
*/
/*
if(attributes.center.y > self.collectionView.frame.size.height)
{
attributes.center = CGPointMake(attributes.center.x, self.collectionView.frame.size.height/2);
}*/
prevNodeCenter = attributes.center;
return attributes;
I have a problem regarding positioning an image according to the touches location, however limited to a circle.
It works for the most part, but if the angle (from the touches location to the desired location) is less than 0, it positions the image on the wrong side of the circle.
Perhaps it's some maths that I've done wrong.
Anyway, here's the code:
float newHeight, newWidth, centerPointX, centerPointY;
newHeight = -(invertedY.y - (view.frame.origin.y+view.frame.size.height/2));
newWidth = -(invertedY.x - (view.frame.origin.x+view.frame.size.width/2));
float tangent = newHeight/newWidth;
float calculatedAngle = atanf(tangent);
float s, c, d, fX, fY;
d = view.frame.size.width/2+30;
if (calculatedAngle < 0) {
s = sinf(calculatedAngle) * d;
c = cosf(calculatedAngle) * d;
} else {
s = -sinf(calculatedAngle) * d;
c = -cosf(calculatedAngle) * d;
}
fX = view.center.x + c;
fY = view.center.y + s;
[delegate setPoint:CGPointMake(fX, fY)];
NSLog(#"angle = %.2f", calculatedAngle);
Any help appreciated.
I think the best way to limit location to a circle is calculate vector from center to touch location. Calculate vector length then divide it by that length so it would be normalized. Then multiply normalized vector by radius of circle and finally add this vector to the center to compute new location.
CGPoint touch, center;
CGPoint vector = CGPointMake(touch.x-center.x, touch.y-center.y);
float length = sqrtf(vector.x*vector.x + vector.y*vector.y);
// Normalize and multiply by radius (r)
vector.x = r * vector.x / length;
vector.y = r * vector.y / length;
[delegate setPoint:CGPointMake(center.x + vector.x, center.y + vector.y)];
I'm trying to get some basic OpenGL-ES with Shaders to run on the iPhone, based on some examples.
For some reason my projection matrix refuses to result in something on the screen. It feels like a clipping plane is set very near but that contradicts with the values I supply. If I render the same scene with an Orthogonal projection matrix I see my object just no perspective obviously.
Here's the code that generates the projection matrix:
esPerspective(&proj, 45.f, 768.0/1024.0, 1.f, 10000.f);
void esPerspective(ESMatrix *result, float fovy, float aspect, float nearZ, float farZ)
{
float frustumW, frustumH;
frustumH = tanf( fovy / 360.0f * PI ) * nearZ;
frustumW = frustumH * aspect;
esFrustum( result, -frustumW, frustumW, -frustumH, frustumH, nearZ, farZ );
}
void esFrustum(ESMatrix *result, float left, float right, float bottom, float top, float nearZ, float farZ)
{
float deltaX = right - left;
float deltaY = top - bottom;
float deltaZ = farZ - nearZ;
ESMatrix frust;
if ( (nearZ <= 0.0f) || (farZ <= 0.0f) ||
(deltaX <= 0.0f) || (deltaY <= 0.0f) || (deltaZ <= 0.0f) )
return;
frust.m[0][0] = 2.0f * nearZ / deltaX;
frust.m[0][1] = frust.m[0][2] = frust.m[0][3] = 0.0f;
frust.m[1][1] = 2.0f * nearZ / deltaY;
frust.m[1][0] = frust.m[1][2] = frust.m[1][3] = 0.0f;
frust.m[2][0] = (right + left) / deltaX;
frust.m[2][1] = (top + bottom) / deltaY;
frust.m[2][2] = -(nearZ + farZ) / deltaZ;
frust.m[2][3] = -1.0f;
frust.m[3][2] = -2.0f * nearZ * farZ / deltaZ;
frust.m[3][0] = frust.m[3][1] = frust.m[3][3] = 0.0f;
esMatrixMultiply(result, &frust, result);
}
My projection matrix comes out as:
[3.21, 0, 0, 0]
[0, 2.41, 0, 0]
[0, 0, -1, -1]
[0, 0, -2, 0]
Even if I manually set the [3][3] cell to 1 I still don't see anything.
Any ideas?
Swap your rows and columns over (ie transpose).
Well your projection matrix is transposed either way. You have a row major projection matrix ...