I want to draw a rectangle shape using cocos2d-android . i googled all my way to draw the rectangle in my scene and trying
CGRect rect = CGRect.make(numbers[0][0],numbers[0][1],70,70);
but it was not displaying any rectangle. could any one help me out to draw a rectangle in scene?
Check out the example file for drawing primitives. You can see an example of drawing a arbitrary polygon there:
// closed purple poly
gl.glColor4f(1.0f, 0.0f, 1.0f, 1.0f);
gl.glLineWidth(2);
CCPoint vertices2[] = {CCPoint.ccp(30, 130), CCPoint.ccp(30, 230), CCPoint.ccp(50, 200)};
Primitives.drawPoly(gl, vertices2, 3, true);
Just define your rectangle points there.
There are a lot more test examples to be found there that can answer the basic drawing questions like this.
Related
I'm struggeling to understand how the rendering works in OpenGL.
In my render function, I want something like this...
void Window::render() {
//Render scene
//set screen center to be 0,0 (like opengl is by default)
myObject.render();
//Render interface
//set point 0,0 to topleft corner so that I can render this based om screensize
myInterface.render();
EDIT: My question is, how do I do it? I've tried fiddeling around with:
glMatrixMode(GL_PROJECTION);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
This is a code I use to draw rectangle in my program:
glBegin(GL_QUADS);
glTexCoord2f(0.0f, maxTexCoordHeight); glVertex2i(pos.x, pos.y + height);
glTexCoord2f(0.0f, 0.0f); glVertex2i(pos.x, pos.y);
glTexCoord2f(maxTexCoordWidth, 0.0f); glVertex2i(pos.x + width, pos.y);
glTexCoord2f(maxTexCoordWidth, maxTexCoordHeight); glVertex2i(pos.x + width, pos.y + height);
glEnd();
It draws just a simple rectangle with specified texture, e.g. like this:
I'd like to ask if it's possible in OpenGL to achieve border effect like this:
As you see inside this tile there's just a plain blue background which could be handled separately - just automatically resized texture. This can be achieved easily with a code snippet I gave, but the problem is with border.
If the border was supposed to be one color, I could try drawing empty, not-filled rectangle by using GL_LINES around my texture, but it's not.
Also if tiles were always with a fixed size, I could prepare a texure that would match it, but they HAVE TO be easily resizable without changing a bitmap file I use as texture.
So if it's not possible with basic OpenGL functions, what are the approaches to achieve this effect that would be most efficient and/or easy?
EDIT: It has to be 2D.
This is a classical problem of GUIs with OpenGL and is often solved using the 9-cell-pattern. In this, you add the effect to the original image (or define it by other opengl-parameters) and split the rendered quad in nine quads: three rows and three columns.
You then make the height of the upper and bottom row fixed, as you make the width of the left and the right column fixed. The center quad is scaled so that your object fits the rectangle you want to fit. You then map only the border parts of the texture to the quads forming the outer cells, while you map the center of the texture to the center quad.
Related to what was said in the comments, you could also use actual 3D effects by making the quad 3D. Noone forces you to use perspectivic projection in that case, you can stay with Orthogonal projection (2D-Mode). OpenGL will always do 3D-calculations anyways.
Aside from Jonas's answer, which is excellent, I want to add two more options.
The first one is to just make the texture look like your desired square. No fancy code necessary if you can do it in photoshop ;).
The second one is to complicate your drawing code a bit. If you look at your image you can see that every "side-slope" of your square can be drawn with two triangles. You can make your code draw 10 triangles instead of one square and use a different color for each group of two triangles:
draw() {
GLFloat i = <your_inset_here>;
//top border part, top left triangle
glColor3f(<color_0>);
glVertex2f(pos.x, pos.y);
glVertex2f(pos.x + w, pos.y);
glVertex2f(pos.x + i, pos.y + i);
//top border part, bottom right triangle
glVertex2f(pos.x + w, pos.y);
glVertex2f(pos.x + w - i, pos.y + i);
glVertex2f(pos.x + i, pos.y + i);
//repeat this process with the other coordinates for the other three borders
// draw the middle square using {(pos.x+i,pos.y+i),(pos.x+w-i,pos.y+i),(pos.x+w-i,pos.y+h-i),(pos.x+i,pos.y+h-i)} as coordinates
}
You can further improve this by creating a function to draw an irregularly shaped quad with the give coordinates and a color and call that function 5 times.
I am creating a 3D game. I have objects in my game. When an enemy hits my position I want my screen to go red for a short time. I have chosen to do this by trying to render a full screen red square at my camera position. This is my attempt which is in my render method.
RenderQuadTerrain();
//Draw the skybox
CreateSkyBox(vNewPos.x, vNewPos.y, vNewPos.z,3500,3000,3500);
DrawCoins();
CollisionTest(g_Camera.Position().x, g_Camera.Position().y, g_Camera.Position().z);
DrawEnemy();
DrawEnemy1();
//Draw SecondaryObjects models
DrawSecondaryObjects();
//Apply lighting effects
LightingEffects();
escapeAttempt();
if(hitbyenemy==true){
glEnable(GL_BLEND);
glBlendFunc(GL_ONE, GL_ONE); // additive blending
float blendFactor = 1.0;
glColor3f(blendFactor ,0,0); // when blendFactor = 0, the quad won't be visible. When blendFactor=1, the scene will be bathed in redness
glBegin(GL_QUADS); // Draw A Quad
glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glEnd();
}
All this does, however, is turn all of the objects in my game a transparent colour, and I can't see the square anywhere. I don't even know how to position the quad. I'm very new to openGL.
How my game looks without an attempt to render a quad:
How my game looks after my attempt:
With Kevin's code and glDisable(GL_DEPTH_TEST);
EDIT: I have changed the code to the below paste..still looks like image 1.
http://pastebin.com/eiVFcQqM
There are several possible contributions to the problem:
You probably want regular blending, not additive blending; additive blending will not turn white, yellow, or purple objects red. Change the blend func to glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); and use a color of glColor4f(1, 0, 0, blendFactor);
You should glDisable(GL_DEPTH_TEST); while drawing the overlay, to prevent it from being hidden by other geometry, and reenable it afterward (or use glPush/PopAttrib(GL_ENABLE_BIT)).
The projection and modelview matrixes should be the identity, to ensure a quad with those coordinates covers the entire screen. (However, you may have that implicitly already, since you say it is affecting the full screen, just not in the right way.)
If these suggestions do not fix it, please edit your question showing screenshots of your game with and without the red flash so we can understand the problem better.
I am looking for a technique in OpenGL that I can use in order to map color points on a surface.
Each point is defining a display color and three coordinates (X, Y, Z).
The surface on which to map those data is built from all the points' coordinates in the main usage (complex shape) but can be built normally from standard shape such as a cone or a sphere.
Since there are voids between the points (for example one millimeter step between two points along the X axis), it would be also needed to interpolate the points data on the surface.
I am thinking about building bitmaps from the points and then applying those bitmaps on my surfaces but I am wondering if OpenGL does have a feature that allow to do that in a "smart way".
It sounds to me like what you are asking for is basic OpenGl behaviour.
If you draw a triangle:
glBegin(GL_TRIANGLES);
glColor3f(1.0f,0.0f,0.0f); // Red
glVertex3f( 0.0f, 1.0f, 0.0f); // Top vertex
glColor3f(0.0f,1.0f,0.0f); // Green
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom left vertex
glColor3f(0.0f,0.0f,1.0f); // Blue
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom right vertex
glEnd();
The result is a smoothly ( if garishly) coloured solid triangle.
So your problem is to construct a series of polygons (possibly just triangles) which cover your surface and have the point set as vertices.
For a great intro to OpenGl, see NeHe's tutorials, including the above example.
I'm new to Direct3D and I was on a project taking pictures from a webcam and draw some 3D objects in front of it.
I was able to render webcam images as background using Orthogonal Projection.
//init matrix
D3DXMatrixOrthoLH(&Ortho, frameWidth, frameHeight, 0.0f, 100.0f);
//some code
D3DXVECTOR3 position = D3DXVECTOR3(0.0f, 0.0f, 100.0f);
g_pSprite->Begin(D3DXSPRITE_OBJECTSPACE);
g_pSprite->Draw(g_pTexture,NULL,¢er,&position,0xFFFFFFFF);
g_pSprite->End();
Then I tried to insert a simple triangle in front of it. The Matrices are setup as follow
D3DXMATRIXA16 matWorld;
D3DXMatrixTranslation( &matWorld, 0.0f,0.0f,5.0f );
g_pd3dDevice->SetTransform( D3DTS_WORLD, &matWorld );
D3DXMATRIXA16 matProj;
D3DXMatrixPerspectiveFovLH( &matProj, D3DX_PI / 4, 1.0f, 1.0f, 100.0f );
g_pd3dDevice->SetTransform( D3DTS_PROJECTION, &matProj );
5.0 should be < 100.0 and the triangle is supposed to be appear in front of the images. However it does not appear unless set the z position to 0. At position 0, i can see the triangle but background is blank.
Do you guys have any suggestions?
I would not draw the webcam image in the object space (D3DXSPRITE_OBJECTSPACE) if you intend to use your image solely for background purpose; something like
D3DXVECTOR3 backPos (0.f, 0.f, 0.f);
pBackgroundSprite->Begin(D3DXSPRITE_ALPHABLEND);
pBackgroundSprite->Draw (pBackgroundTexture,
0,
0,
&backPos,
0xFFFFFFFF);
pBackgroundSprite->End();
should hopefully do what you're looking for.
As a quick fix you could disable depth testing as follows;
g_pd3dDevice->SetRenderState(D3DRS_ZENABLE, D3DZB_FALSE);
This way the z-index of the primitives being drawn should reflect the order in which they are drawn.
Also, try using the PIX debugging tool (this is bundled with the DirectX SDK). This is always my first port of call for drawing discrepancies as it allows you to debug each Draw call separately with access to the depth buffer and transformed vertices.