3d

[3D图形学]视锥剔除入门(翻译)

由 允我心安 提交于 2021-02-12 22:32:25
原文: http://www.flipcode.com/archives/Frustum_Culling.shtml 时至今日,许多刚刚下海的3D引擎程序员仍不了解视锥剔除(Frustum Culling)的重要性和益处,这让我和我的小伙伴们感到很震♂惊.我在Flipcode的论坛中发现尽管网络上有海量的相关资料,仍有许多人提出对视锥剔除实现的问题.因此我决定撰写这篇文档,简单描绘出我现在所使用的四叉树剔除引擎(Quad-tree Culled Engine)的工作方式.诚然,市面上有许多种成熟且高效的视锥剔除算法,但我认为这个算法足以用来学习视锥剔除的理论基础.在正式开始前我还想说明一件事,以前我一直把Frustum(平截头体)打成Frustrum(截头锥),为此我没少被论坛上的人喷.在这里我承认Frustum是正确的拼写.对那些以前被我冒犯的人我表示抱歉...你们这群吹毛求疵的傻[哔-]... 大多数人已经知道什么是视锥剔除了(译者:如果你是手滑误点进来的...视锥剔除是一个图形渲染前的步骤,用于剔除掉不需要绘制的部分).视锥(准确说是平截头体Frustum)的形状酷似一个塔尖被削平了的金字塔,更准确地说,是一个四棱锥的顶点偏下位置被一个裁面(Clipping Plane,见图1)裁断.事实上,视锥本身就是由6个面所组成.这6个面被称为近裁面,远裁面,上裁面,下裁面,左裁面

Java 3D: Where can I insert a “post rendering” FX?

由 心已入冬 提交于 2021-02-11 15:59:43
问题 I extended a Canvas3D and then I override the method "postSwap()", but my odd-even line effect is flickering a lot, what could be another good point for inserting this process? public void postSwap() { Graphics2D g2 = (Graphics2D)this.getGraphics(); Map map = new HashMap(); map.put(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_OFF); g2.addRenderingHints(map); g2.setColor(WipideaApplet.BCK2); int h = this.getHeight(), w = this.getWidth(); for (int i=0;i<h;i++) { if (i%2==0)

R: Kernel Density Plots (Bandwidth Must be Strictly Positive)

由 烂漫一生 提交于 2021-02-11 12:38:03
问题 I am using the R programming language. I am following this tutorial over here for making 3d kernel density plots in R: https://plotly.com/r/3d-surface-plots/: library(MASS) library(plotly) kd <- with(MASS::geyser, MASS::kde2d(duration, waiting, n = 50)) fig <- plot_ly(x = kd$x, y = kd$y, z = kd$z) %>% add_surface() fig I decided to try this on my own data : #generate data a = rnorm(100,10,10) b = rnorm(100,5,5) c = rnorm(100,5,10) d = data.frame(a,b,c) #make 3d plot (I think n = 50 refers to

Plotting 3D brain image Python

由 自古美人都是妖i 提交于 2021-02-11 12:28:43
问题 I have a data set of brain which is in .nii.gz format to work on neural network I used nilearn package to read the file and get the image data. The shape of the image is (256, 256, 150) I can plot the 2D image from slicing the image using Matplotlib but, How can I plot the image in 3D using Python Thanks 来源： https://stackoverflow.com/questions/62256355/plotting-3d-brain-image-python

JavaFX 8 - How to set NearClip and FarClip on a Parallel Camera?

由 六月ゝ 毕业季﹏ 提交于 2021-02-10 22:51:50
问题 I am part of a team building an application that manipulates a visual model using JavaFX 8 3D. We use both a Perspective Camera and a Parallel Camera. The Perspective Camera is working as expected. It is currently working with isEyeAtCameraZero false. This was done for maximum compatibility with the Parallel Camera. The Perspective Camera behaves correctly when camera.setNearClip() and camera.setFarClip() are called. The Parallel Camera does not appear to respond to camera.setNearClip() and

How to calculate ray in real-world coordinate system from image using projection matrix?

由 你说的曾经没有我的故事 提交于 2021-02-10 20:38:56
问题 Given n images and a projection matrix for each image, how can i calculate the ray (line) emitted by each pixel of the images, which is intersecting one of the three planes of the real-world coordinate system? The object captured by the camera is at the same position, just the camera's position is different for each image. That's why there is a separate projection matrix for each image. As far as my research suggests, this is the inverse of the 3D to 2D projection. Since information is lost

How to calculate ray in real-world coordinate system from image using projection matrix?

由 ≡放荡痞女 提交于 2021-02-10 20:35:36
问题 Given n images and a projection matrix for each image, how can i calculate the ray (line) emitted by each pixel of the images, which is intersecting one of the three planes of the real-world coordinate system? The object captured by the camera is at the same position, just the camera's position is different for each image. That's why there is a separate projection matrix for each image. As far as my research suggests, this is the inverse of the 3D to 2D projection. Since information is lost

Normals transformation for Back-Face culling

由 别说谁变了你拦得住时间么 提交于 2021-02-10 05:09:54
问题 Starting from this lesson here: WebGL 3D Perspective I am triyng to implement Back-Face culling no magic. I am computing on the fly the face normals in object space. After that, I am setting the fudgeFactor inside m[2][3] to get the perspective divide by Z . To check if the shear matrix works, I expanded my snippet using directly the vertex positions projected out of the WebGL vertex shader, and added the "projected position" flag. Now, I am triyng to use the z-component inside the

Normals transformation for Back-Face culling

由 别说谁变了你拦得住时间么 提交于 2021-02-10 05:08:19
问题 Starting from this lesson here: WebGL 3D Perspective I am triyng to implement Back-Face culling no magic. I am computing on the fly the face normals in object space. After that, I am setting the fudgeFactor inside m[2][3] to get the perspective divide by Z . To check if the shear matrix works, I expanded my snippet using directly the vertex positions projected out of the WebGL vertex shader, and added the "projected position" flag. Now, I am triyng to use the z-component inside the

How may I project vectors onto a plane defined by its orthogonal vector in Python?

由 守給你的承諾、 提交于 2021-02-08 13:43:13
问题 I have a plane, plane A , defined by its orthogonal vector, say (a, b, c) . (i.e. the vector (a, b, c) is orthogonal to plane A ) I wish to project a vector (d, e, f) onto plane A . How can I do it in Python? I think there must be some easy ways. 回答1: Take (d, e, f) and subtract off the projection of it onto the normalized normal to the plane (in your case (a, b, c) ). So: v = (d, e, f) - sum((d, e, f) *. (a, b, c)) * (a, b, c) / sum((a, b, c) *. (a, b, c)) Here, by *. I mean the component
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