to Draw 3D Graphics on a Computer ✦OpenGL: It Works Anywhere, It's Traditional, It's Generic ✦DirectX: Microsoft Platform Specialization ✦Vulkan: A spiritual successor to OpenGL, a low-level API for fi ne control of the GPU ✦Metal: A low-level, low-overhead hardware-accelerated 3D graphic and compute shader API created by Apple 11
(Open Graphics Library) is an industry standard API for hardware-independent 2D and 3D graphics rendering ✦It's cross-platform, and is used in a wide range of fi elds, from visualization of scienti fi c and technological calculations to game development 13
an o ff i cial wrapper, but recent Ruby fails to install the gem ✦https://github.com/larskanis/opengl ✦Looking at the commit log, the last commit was 7 years ago 14 Library for working with OpenGL in Ruby
completely different before and after OpenGL 3.0, so be careful ✦It is better to understand which style is written before reading ✦In the old style, vertex data is sent one by one from the CPU to the GPU and drawn between the instruction blocks glBegin() and glEnd() ✦In the modern standard method, the vertex data is transferred to a memory area on the GPU called Vertex Buffer Object, and the shader is executed on the GPU, which allows fi ne control of the drawing process 15 Reading the sample code Tips
peripheral functions needed to use OpenGL ✦It also abstracts OS-speci fi c processing ✦OpenGL is a drawing engine ✦GLFW/GLUT is a toolkit to interface with the platform 17 GLFW / GLUT Application GLFW or GLUT Graphics Driver OpenGL
✦A library developed in the 90s that features a simple API ✦Provides windowing, event handling, and basic drawing functions ✦Good for learning, but no longer in development ✦The original hasn't been maintained for over 20 years 18 GLUT
modern libraries introduced in 2002 ✦Support for multiple windows and monitors ✦Finer event control ✦Support for OpenGL 3.x/4.x, Vulkan, Metal, and other modern APIs 20 GLFW
uses four pieces of information to manage the position of a single point: ✦Homogeneous coordinates (x, y, z, w) ✦"Why do you need four pieces of information in three dimensions?" ✦For smooth computation of "projections" 32
types of coordinate systems ✦A right-handed coordinate system is positive in front of the z-axis and negative in the back of the z-axis ✦A left-handed coordinate system is negative in front of the z-axis and positive in the back of the z-axis 33 Point Location y +z x -z y -z x +z
types of coordinate systems ✦A right-handed coordinate system is positive in front of the z-axis and negative in the back of the z-axis ✦A left-handed coordinate system is negative in front of the z-axis and positive in the back of the z-axis 34 Point Location y +z x -z y -z x +z
drawing? 36 ✦De fi ne vertices ✦"This geometry consists of the coordinates (x1, y1, z1), (x2, y2, z2) and ..." and teach vertex position information ✦De fi ne primitives ✦"Draw a triangle using the previous vertex." and specify the type of primitive ✦Rendering ✦Convert de fi ned primitives into a form that can be displayed on the computer screen
GLFW.WindowShouldClose(window) = = GLFW : : TRUE GL.Begin(GL : : TRIANGLES) GL.Vertex2f(-0.8, -0.8) GL.Vertex2f(0.8, -0.8) GL.Vertex2f(0.0, 0.9) GL.End GLFW.SwapBuffers(window) GLFW.PollEvents() end Signal that you have fi nished drawing the triangle
Matrix GLFW.GetFramebufferSize(window, width_buf, height_buf) width = width_buf.unpack('I').f i rst height = height_buf.unpack('I').f i rst height = 1 if height = = 0 aspect = width.to_f / height.to_f GL.MatrixMode(GL : : PROJECTION) GL.LoadIdentity() fovy_degrees = 45.0 near_clip = 0.1 far_clip = 100.0 fovy_radians = fovy_degrees * Math : : PI / 180.0 top = Math.tan(fovy_radians / 2.0) * near_clip bottom = - top right = top * aspect left = - right GL.Frustum(left, right, bottom, top, near_clip, far_clip) Set the vertical fi eld of view to determine how wide the camera can see
matrix used to transform an object's coordinates in world space into camera space ✦Model Matrix ✦Matrix for transforming vertex data based on position, rotation, and scale in the world coordinate system ✦View Matrix ✦Matrix for de fi ne the position and orientation of the camera and transform world space coordinates into camera space Model-View Matrix 65
Matrix GL.MatrixMode(GL : : MODELVIEW) GL.LoadIdentity() GL.Translatef(0.0, 0.0, -9.0) GL.Rotatef(rotation_angle, 1.0, 1.0, 0.0) rotation_angle += 0.5 Declare that we are about to operate on a model view matrix and initialize the matrix
Matrix GL.MatrixMode(GL : : MODELVIEW) GL.LoadIdentity() GL.Translatef(0.0, 0.0, -9.0) GL.Rotatef(rotation_angle, 1.0, 1.0, 0.0) rotation_angle += 0.5 Move the camera back 9.0 in the positive z-axis
3D objects on the screen in the correct position and shape ✦But it still looks like a fl at, shadowless picture ✦The last important element that adds reality is lighting and materials ✦They simulate how light bounces off the surface of an object and reaches our eyes Lighting and Materials 75
sources ✦Ambient light ✦Indirect light that illuminates the entire surface evenly ✦Helps prevent shadows that do not shine directly into the light source from going black ✦Diffuse re fl ection ✦Re fl ection where light from a source scatters evenly across the surface of an object ✦Determines the brightness of illuminated surfaces ✦Specular re fl ection ✦A light source that re fl ects strongly in a particular direction ✦Produces a gloss 78
OpenGL make it easy to draw 3D graphics ✦It's also a great way to learn the basics of 3D graphics ✦The world of 3D graphics is a deep and exciting fi eld to explore ✦I hope this talk will be your fi rst step into this exciting world!
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