CS482 Lab Session 2HelloOpenGL3D

2019. 9. 19

HelloOpengl3D• Fork or download ‘HelloOpenGL3D’

https://github.com/KAIST-VCLAB/cs482-2019-master

• Run the application• HelloOpenGL3D

– 3 buttons (world/cube1/cube2)– a cube– a square

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Structure

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HelloOpengl3D

• MainActivity class– configures layout and view

• MyGLSurfaceView class– renderer manager– handles touch event

• MyGLRenderer class– responsible for making OpenGL calls to

render a frame

• Cube class– stores vertex position and normal

• Square class– stores vertex position and normal

MainActivity

MyGLSurfaceView

MyGLRenderer

Cube

Square

MainActivity• In Android, an activity represents a single screen with a user interface.

• onCreate()– When an activity begins, onCreate() is called once.– Put all initialization codes in onCreate().

• onResume()– onResume() is called right before the activity shows up.– Put codes for getting ready here. (e.g., re-allocating)

• onPause()– onPause() is called when another activity comes into the foreground.– Put codes for relaxing here. (e.g., de-allocating)

• For more information:– https://developer.android.com/training/basics/activity-lifecycle/starting.html– https://developer.android.com/reference/android/app/Activity.html– http://www.tutorialspoint.com/android/android_acitivities.htm

MainActivity

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OnCreate()OnStart()OnResume()

OnPause() OnResume() OnPause()OnStop()

MyGLSurfaceView• A subclass of ‘GLSurfaceView’

• GLSurfaceView– For displaying OpenGL rendering.– A GLSurfaceView provides the following features:

• Manages a surface, which is a special piece of memory that can be composited into the Android view system.

• Manages an EGL display, which enables OpenGL to render into a surface.• Accepts a user-provided Renderer object that does the actual rendering.• Renders on a dedicated thread to decouple rendering performance from

the UI thread.• Supports both on-demand and continuous rendering.• Optionally wraps, traces, and/or error-checks the renderer's OpenGL calls.

• onTouchEvent() handles touch events from user

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mRenderer = new MyGLRenderer();setRenderer(mRenderer);

MyGLRenderer• A subclass of ‘GLRenderer’

• GLRenderer– A generic renderer interface.– The renderer is responsible for making OpenGL

calls to render a frame.– GLSurfaceView clients typically create their own

classes that implement this interface, and then call setRenderer() to register the renderer with the GLSurfaceView.

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@Overridepublic void onDrawFrame(GL10 unused) {

Cube, Square• Custom classes for 3D objects.

• Store 3D positions and normal vectors of vertices.• Attach shaders– add the vertex shader and face shader from files

(.vshader, .fshader)

• Do routines for OpenGL rendering

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Cube

Square

int vertexShader = MyGLRenderer.loadShaderFromFile(GLES20.GL_VERTEX_SHADER, "basic-gl2.vshader");

int fragmentShader = MyGLRenderer.loadShaderFromFile(GLES20.GL_FRAGMENT_SHADER, "diffuse-gl2.fshader");

Implementation

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MainActivity

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MyGLSurfaceView

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MyGLRenderer

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MyGLRenderer

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Task• Add a new Cube next to the old one• Implement rotation/translation w.r.t.

– World– Cube1– Cube2

• Rotation by touching with a finger• Translation by touching with two fingers

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Add a cube Rotate (world) Rotate (cube1) Translation (cube1)

Hints• You only need to modify..– onTouchEvent(..) in MyGLSurfaceView.java– onDrawFrame(..) in MyGLRenderer.java– onSurfaceCreated(..) in MyGLRenderer.java

• Try to make use of the matrix library.– Matrix.setIdentityM(..)– Matrix.translateM(..)– Matrix.rotateM(..)– Matrix.multiplyMM(..)

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More Hints• You have to modify model-view matrices that are used when yo

u draw a square and cubes.• Modify them using dx and dy from onTouchEvent(..) function.

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// DrawmSquare.draw(mProjMatrix, mSquareModelViewMatrix, mSquareNormalMatrix, mLight, mLight2);mCube.draw(mProjMatrix, mCubeModelViewMatrix, mCubeNormalMatrix, mLight, mLight2);

No More Hints

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