Just put a - void drawRect: All this abstract stuff is nice, but how does it look when it works? They should give you some idea how to put all of this together. The first was Appendix A: It goes through a detailed account of creating a custom NSView by subclassing it and then creating the files needed to interface with it in the Objective-c app that they create in Project Builder.
Also, pay special attention to anything relating to the method - void drawRect: NSRect rect;. The second source that I used was OpenGL: Programming Guide , third edition. The examples in it work as is or with little modification on OS X. For example, the code snippet on pg. Here is the project in a zip for example. If something in this tutorial is not clear, drop me a line on Twitter TGeneDavis. Who is this tutorial for?
How to Use This Document
What does this tutorial cover? Programming Guide" third edition, pg 6. Gene Davis Software. The OpenGL command glFlush draws the content provided by your routine to the view. Add the code to perform your drawing. In your own application, you'd perform whatever drawing is appropriate. But for the purpose of learning how to draw OpenGL content to a view, add the code shown in Listing This code draws a 2D, gold-colored triangle, whose dimensions are not quite the dimensions of a true golden triangle, but good enough to show how to perform OpenGL drawing.
Make sure that you insert this routine before the drawRect: Resize the view to fit the window. Open the Attributes pane of the inspector for the view, and take a look at the renderer and buffer attributes that are available to set. These settings save you from setting attributes programmatically. Only those attributes listed in the Interface Builder inspector are set when the view is instantiated.
If you need additional attributes, you need to set them programmatically. Build and run your application. You should see content similar to the triangle shown in Figure Replace the immediate-mode drawing commands with commands that persist your vertex data inside OpenGL. In the interface for the view, declare a variable that indicates whether the view is ready to accept drawing.
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- Update the Rendering Context When the Renderer or Geometry Changes.
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- Context Parameters Alter the Context’s Behavior.
A view is ready for drawing only if it is bound to a rendering context and that context is set to be the current one. Cocoa does not call initialization routines for objects created in Interface Builder. If you need to perform any initialization tasks, do so in the awakeFromNib method for the view. Note that because you set attributes in the inspector, there is no need to set them up programmatically unless you need additional ones. There is also no need to create a pixel format object programmatically; it is created and loaded when Cocoa loads the nib file.
Programming OpenGL on macOS
Your drawRect: You need to provide code that handles the case when the view is not ready to draw into. OpenGL is at its best when doing real-time and interactive graphics. Your application needs to provide a timer or support user interaction. This section provides an overview of the key tasks you need to perform to customize the NSView class for OpenGL drawing. When you subclass the NSView class to create a custom view for OpenGL drawing, you override any Quartz drawing or other content that is in that view.
You need to override the update and initWithFrame: The values are interpolated between the vertices for each pixel. Our fragment shader outputs colours for our fragments. We must declare the output variable as well. We then define our program, which tells OpenGL to simply pass the interpolated colour through as the colour of the fragment:. Our shader program is plain text at the moment. Clearly we need to compile it and link it.
OpenGL Programming Guide for Mac
Because we need our code to run on such heterogenious hardware, we compile and link the shader program at runtime. If we successfully compiled the code, we create a program, add the vertex and fragment shaders to it. We then tell OpenGL which of our colour buffers to put the fragment shader's output in. By specifying 0 we ask for the 0th colour buffer, which by default is the back buffer for our view:. Once we have linked the program, we ask OpenGL to tell us about the uniforms and attributes in our programs. We'll use these values later to tell OpenGL which bits of our mesh data mean what.
Finally, we delete the temporary compiled object code, as we've now successfully linked it into a shader program. Lets look at how we compile the vertex and fragment shaders now. We now ask OpenGL to give us back the compiler log, and print it out. This will help with debugging if we made a mistake writing our shader:. While the info log is interesting, the compile status is what tells us whether we succeeded in compiling the code or not.
We make sure we were successful, and return our reference to the object code:. Linking follows a similar pattern. We ask OpenGL to link the program, print out the linker log, and then check the link status to make sure everything went well.
In this simple example we define our quad as an array of data in our source file. Normally you would do this by loading a model file of some sort, but for just drawing a quad we'll take a short cut:. The array of vertex data is all very well, but it's not where we want it. It's stored in system RAM, instead, we want to put it on the graphics card. To get OpenGL to store this data on the graphics card we first ask for a Vertex Array Object - this gives us a method of quickly setting up our buffer and vertex array states.
We bind the vertex array object so that future calls will affect this VAO:. We then ask for a Vertex Buffer Object to store the data in. We tell OpenGL that future calls relating to the array buffer will be talking about the buffer we just created:. Finally we upload the data. We tell OpenGL that the data is static we're not going to modify it lots , and we're going to use it for drawing:.
Remember when we asked OpenGL to tell us about the attributes in our program? Now we need to tell OpenGL how to map those attribute locations onto the data we just uploaded. First, we tell OpenGL to enable the attributes:. Now we tell OpenGL where in the currently bound buffer to find the data.
First, we tell it about the positions. They have 4 components, each of which is a floating point value. We don't want to normalise the data. The data is spaced out by the size of our Vertex data structure, and you can find the first one at the offset of the position in that data structure. With all that data on the graphics card, we now need to make use of it. Each time we render, we start by clearing the screen to black. First we tell OpenGL that black is the right colour to clear to:. Next, we need to tell OpenGL where we want the quad to be rendered this frame.
To make the quad move in a circle we use the sine and cosine of the time:. Finally, we tell OpenGL to actually draw the data in our array. We draw a triangle fan, and provide the 4 vertices in buffer.
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