I have got a small question while coding. I want to draw a cube, using GLUT in C++. Im using the window to viewport transformation to draw the cube in the middle of the screen.
Now the viewport window has a size, and if I move the cube in the viewport it moves fine, however it leaves or "hangs out" from the side of the viewport window.
How could I make that if some parts of a cube leave the viewport window then it would disappear?
Drawing in the rest of the window after i draw the cube in the viewport using GL_POLYGON is not a solution.
Is there a way to create separate "canvases", or something like that in GLUT?
Found my answer using glScissor.
Related
I'm trying to do something like what Auslogics Disk Defrag does with its custom window:
As can be seen, the blurred semi transparent shadow surrounding the window is much darker than the standard one, so the program must be drawing it by itself. The problem is, I can't find a way to paint anything transparent around a window.
In an answer to a similiar question, someone suggested creating a slightly bigger transparent window (using WS_EX_LAYERED + SetLayeredWindowAttributes()) behind the actual application window, and then do the translucent drawing on the transparent one. Not only does it sound like an ugly hack, it doesn't actually work. If, for example, one tries to draw a semi transparent black rectangle on a transparent window via GDI+, alpha blending is applied to the shape's color over the window background color (which would also be the transparency color) and then the shape is drawn with the calculated color, which obviously is not the window transparency, resulting in an opaque rectangle.
The semi transparent shadow is actually done by Gaussian Blur of the black square.
You can use this effect to create glows and drop shadows and use the
composite effect to apply the result to the original image. It is
useful in photo processing for filters like highlights and shadows.
You can use the output of this effect for input into lighting effects,
like the Specular Lighting or Diffuse Lighting effects, because the
alpha channel is blurred, too and lighting effects use the alpha
channel to determine surface geometry as a height map.
This effect is used by the built-in Shadow effect.
Refer: Gaussian blur effect
Then remove the standard frame, the entire window is your client area, so you can draw shadow in the extended frame.
Refer: Drawing in the Extended Frame Window
I think I've found a solution that works for me. I was hoping I wouldn't have to create an extra window just for the shadow, but every method I could find or think of would require me to draw all the controls by myself and/or somehow correct their alpha values.
So, I'm using a layered window with per pixel alpha. I paint over it with Direct2D, or, alternatively, I use some PNGs with transparency for the edges and corners of the shadow and copy them on a memory DC. Either way I simply recreate the shadow with the right dimensions when the window is resized, and call UpdateLayeredWindowIndirect. Both methods seem to be working well on Windows 7 and 10, and so far I haven't found any glitches.
Preventing it from showing on the taskbar was a bit tricky. All the ways I know have drawbacks. What worked best for me was making the layered window owned by the main one. At least that way it will only be visible on the desktop where the program is actually running, unlike other alternatives which would force it to show on every virtual desktop. Finally, because I disable that window, I interact with it by processing WM_SETCURSOR.
I've inherited a project which renders a 3D scene directly to the window using OpenGL. The code works fine, but we're now drawing an icon onto the 3D view to "Exit 3D view mode". This also works fine, but results in a lot of flickering as the view is rapidly rotated.
I'd like to be able to draw to an off-screen bitmap (ie. without a HWND), then draw my icon to the bitmap, then finally StretchBlt the bitmap to the window using double-buffering. We do this in other contexts (such as zooming into an image which does not need OpenGL) and it works great. My problem is that I am an OpenGL novice and all attempts at starting with the DC of the off-screen bitmap and creating a HWND from this DC fail, usually because of selecting a pixel format for the DC.
There are a few questions asking similar things here on StackOverflow (eg. this question without an accepted answer. Is this possible ? If so is there a relatively straightforward tutorial describing the procedure? If the process is extremely complex requiring detailed OpenGL knowledge, then I may just have to leave it and live with the flickering because it is a rarely used mode in our software.
Just draw the Icon using OpenGL using a textured quad.
All this draw to a bitmap copy to DC StretchBlt involves several roundtrips from and to graphics memory (wastes bandwidth) and StretchBlt will likely not be GPU accelerated. All in all what you want to do is inefficient and may even reduce quality.
I presume you have the icon stored in your executable as a resource. The most simple way to go about it is to create a memory DC (CreateCompatibleDC) with a DIBSECTION (CreateDIBSection), draw the icon to that and load the DIBSECTION data into a OpenGL texture. Then to draw the icon use glViewport to select the destination rectangle in window coordinates, use an identity transform to draw a rectangle covering the whole viewport (position values (-1,1)→(1,1), texture coordinate values (0,0)→(1,1) gives you the right outcome).
Important side fix: In case your program does silly things like setting viewport and the fixed function pipeline GL_PROJECTION matrix in a window resize handler you should clean up that anti pattern and move this to where it belongs: In the drawing code.
I'm working on a project using JOGL API.
Now I am stuck at a point that is the followed:
-I run the program and it shows a Canvas divided in 4 viewPorts. The objective of the project is basically in each of the viewPorts we need to "project" an object from 4 diferent points of view. But first, we need to when clicking [1,2,3,4] to "expand"/"full-screen" the matched ViewPort.
My idea is when clicking any number create a new viewPort like this:gl.glViewport(0, 0, CANVAS_WIDTH, CANVAS_HEIGHT). But this only creates a new viewPort with the size of the canvas.
How can I expand the "content" of any of the 4 viewPort to "enter" that new viewPort?
I think you've got confused what glViewport does. I don't know what you think it does (not), but what it's specified to do is, to set the portion of the OpenGL window, to which to map the post-projection (NDC) space. Or in layman terms, you use it to determine where in the window things get drawn. If you want to render full screen: Make the window full screen and set the viewport to the window size.
If you want to "expand" an existing drawing, you have to set the proper viewport and redraw the parts in question.
I use OpenGl. I would like to create a menu-control, but for this I need a constant resolution-control. I mean that I can set the position of a button by giving a coordinate, in 1024x768. But what if my window doesn't in it. And in full screen mode I hasn't found a method to change the resolution, nevertheless I can get it. So I got the screen width/height, the window width/height and 4 coordinates in 1024x768 for a rectangle. What should I do?
I'm taking a computer graphics course this semester at college and our first assignment is to build a program that works much like Microsoft paint. We need to set options for drawing with shapes of different colors, sizes, and transparency parameters.
I'm having trouble finding information on how to program the ability to draw with a given shape on mouse drag. I'm not asking for the solution in code, but guidance on where to study functions that might accomplish this.
I'm completely new to OpenGL (but not C++) & I own "Computer Graphics with OpenGL" 4th ed. by Hearn & Baker. None of the topics suggest this capability.
What's probably asked from you is creating a single bufferd window, or switching to draw on the front buffer, and draw some shape at the mouse pointers location, when a button is pressed (and dragged), without clearing the frontbuffer inbetween. For added robustness draw to a Frame Buffer Object attached texture, so that dragging some window will not coorupt the user's drawing.
Keywords: Set Viewport to Window size. Ortho projection to window bounds, do not use glClear (except for resetting the picture).