One Frame Animation

SkeletalMesh->PlayAnimation(MyAnim, false);
SkeletalMesh->bPauseAnims = true;
UAnimSingleNodeInstance* Inst = Cast<UAnimSingleNodeInstance>(AnimInstance);
if ( Inst )
{
    Inst->SetPosition(AnimTime);
}

Compile MD5 using openssl on linux

 cc digestMD5.c -o digestMd5 -L/usr/openssl/lib64 -lssl -lcrypto -ldl

I installed openssl into /usr/openssl

Or openssl is located in /opt/openssl

The Greek Alphabet, english pronunciation for math

 https://www.youtube.com/watch?v=PStgY5AcEIw

Baseball terms

심판 - Umpire

투수 - Pitcher

포수 - Catcher

타자 - Batter

지명타자 - Designated hitter

1루수 - First baseman

2루수 - Second baseman

3루수 - Third baseman

유격수 - Shortstop

좌익수 - Left fielder

중견수 - Center fielder

우익수 - Right fielder

중간계투/구원투수 - Bullpen pitcher

마무리투수 - Closer

주자 - Runner

​

눈치채셨겠지만

1루는 First base

2루는 Second base

3루는 Third base 입니다.

공을던지다 - Pitch the ball

공을 치다 - Hit the ball

파울 - foul ball

1루타 - single

2루타 - double

3루타 - triple

내야안타 - infield hit

홈런 - homerun

만루홈런 - grand slam

도루 - Stolen base

볼넷 - base on balls

삼진 - Strike out

직구 - Fast ball

변화구 - Breaking ball

내야 땅볼 - Ground out

직선타구 - Line drive

뜬공 - Fly ball

견제구 - Pick-off throw

땅볼 - Ground ball

VisualStudio : Find a location in Solution Explorer

 Ctrl + [, S

Collision detection : Circle vs Rectangle

detection only

int CheckHit( F_RECT *prcRect1, F_CIRCLE *pcrCircle2 )

{

    int             nResult = false;

    float           ar;

    if ( ( pcrCircle2->x > prcRect1->fLeft   - pcrCircle2->r ) &&

         ( pcrCircle2->x < prcRect1->fRight  + pcrCircle2->r ) &&

         ( pcrCircle2->y > prcRect1->fTop    - pcrCircle2->r ) &&

         ( pcrCircle2->y < prcRect1->fBottom + pcrCircle2->r ) )

    {

        nResult = true;

        ar = pcrCircle2->r;

        if ( pcrCircle2->x < prcRect1->fLeft ) {

            if ( ( pcrCircle2->y < prcRect1->fTop ) )

            {

                if ( ( DistanceSqr( prcRect1->fLeft,  prcRect1->fTop,

                                    pcrCircle2->x, pcrCircle2->y ) >= ar * ar ) ) {

                    nResult = false;

                }

            }

            else {

                if ( ( pcrCircle2->y > prcRect1->fBottom ) )

                {

                    if ( ( DistanceSqr( prcRect1->fLeft,  prcRect1->fBottom,

                                        pcrCircle2->x, pcrCircle2->y ) >= ar * ar ) ) {

                        nResult = false;

                    }

                }

            }

        }

        else {

            if ( pcrCircle2->x > prcRect1->fRight ) {

                if ( ( pcrCircle2->y < prcRect1->fTop ) )

                {

                    if ( ( DistanceSqr( prcRect1->fRight,  prcRect1->fTop,

                                        pcrCircle2->x, pcrCircle2->y ) >= ar * ar ) ) {

                        nResult = false;

                    }

                }

                else {

                    if ( ( pcrCircle2->y > prcRect1->fBottom ) )

                    {

                        if ( ( DistanceSqr( prcRect1->fRight,  prcRect1->fBottom,

                                            pcrCircle2->x, pcrCircle2->y ) >= ar * ar ) ) {

                            nResult = false;

                        }

                    }

                }

            }

        }

    }

    return nResult;

}

대화의 격률

 https://ko.wikipedia.org/wiki/%EA%B7%B8%EB%9D%BC%EC%9D%B4%EC%8A%A4%EC%9D%98_%EB%8C%80%ED%99%94%EA%B2%A9%EB%A5%A0

Unreal Engine's DrawDebugCone

There are two versions of implementation of DrawDebugCone.

One it takes two angles in radians and other one takes degrees. OTL

Order of mov (assembler)

mov ax, 3

which mean move a number 3 into ax register. This is an intel assembler order.

Other assembler use opposite order for instance

mov 3, ax

which is exactly same meanning like shown above.

three types of locks

 1. Try lock

try it only once

2. Spin lock

try forever until it acquires the lock

3. Timeout lock

try it for up to some period of time

UGameplayStatics, Static class with useful gameplay utility functions

 UGameplayStatics, Static class with useful gameplay utility functions

Unreal engine naming conventions

 https://docs.unrealengine.com/4.27/en-US/ProductionPipelines/AssetNaming/

implement add with + operator with racket

 #lang racket

; implement add without + operator

(define add

  (λ (n m)

    (cond

      ((zero? m) n)

      (else (add1

            (add n (sub1

                    m)))))))

One thing I want to notice is that add1 and sub1 are not what I defined myself.

racket basic

 #lang racket

; define a constant

(define myval 3.14)

; function without param

(define myfunc

  (λ ()

    (+ 3 4)))

; call function

(myfunc)

; function with param(which is one formal)

(define myfunc-mul-two

  (λ (x)

    (* 2 x)))

(myfunc-mul-two 4)

; outer function calls inner function

(define double-result-of-f

  (λ (f)

    (λ (z)

      (* 2 (f z)))))

(define add3

  (λ (x)

    (+ 3 x)))

((double-result-of-f add3) 4)

binary search alternative

#include <iostream>

#include <vector>

using namespace std;

int main()

{

    int array[] = { 1,3,3,4,5,5,6,9,10,12,12,15 };

    int n = sizeof(array) / sizeof(int);

    int k = 0;

    int x = 3;

    for (int b = n / 2; b >= 1; b /= 2)

    {

        while (k + b < n && array[k + b] <= x)

        {

            k += b;

        }

    }

    

    if (array[k] == x)

    {

        int a = 10;

    }

}

remainder in racket

 #lang racket

(define remainder

  (λ (x y)

    (cond

      ((< x y) x)

      (else (remainder (- x y) y)))))

unix tree

minnie.tuhs.org/cgi-bin/utree.pl

which on linux

which is used to locate a command. which returns the pathnames of the files (or links) which would be executed in the current environment, had its arguments been given as commands in a strictly POSIX-conformant shell. It does this by searching the PATH for executable files matching the names of the arguments. It does not follow symbolic links.

unreal engine gpu profiling commands

stat gpu

stat rhi

stat unit

ProfileGPU

stdc++

#include <bits/stdc++.h>

using namespace std;

int main()

{

}

stdc++.h allows us to include the entire standard library so I don't need to include each separate header files such as vector, iostream, algorithm and so on.

but it is only for competitive programming not for a professional developer.

use gdbm on ubuntu

First thing you have to do is checking whether gdbm is installed on your system or not.

normally it is installed on /usr/include

find /usr/include *dbm* is the command you can use.

even though gdbm is installed on your machine, you might need to install gdbm_compat if you use ndbm interface.

sudo apt-get install apt-file

apt-file update

apt-file search ndbm.h

then you will see packages that you should install on your machine.

안다는 것

子曰 由, 誨女知之乎. 知之爲知之, 不之爲不知, 是知也

List symbols from object file on linux

 

search all of the symbols in a program. if you can see any of functions beginning of aio_ then for sure it uses async I/O.

curses on linux

 

in case of you have no curses library installed, use 

sudo apt-get install libncurses5-dev

and then compile source code like down below.

cc -o sizeterm sizeterm.c -lncurses

What is a PostgreSQL?

 https://d2.naver.com/helloworld/227936

Linux : find

 find /usr/bin -name "ch*"

not like find/usr/bin -name ch*

// search a file based on the size.

find . -size -600c -ls  // less than 600bytes

find . -size +600c -ls // greater than 600bytes

find . -size 600c -ls // 600 bytes

b -> block

c -> bytes

k -> killo

w -> word

Performance Mantras

Don't do it.

Do it, but don't do it again.

Do it less.

Do it later.

Do it when they're not looking.

Do it concurrently.

Do it more cheaply.

check system swap area

 swapon --show

or use free and see the Swap section.

BloomFilter

Note : BloomFilter in this article is not about rendering filter

False Positive

https://terms.naver.com/entry.naver?docId=862393&cid=50371&categoryId=50371

Good Articles

https://brilliant.org/wiki/bloom-filter/

https://www.youtube.com/watch?v=V3pzxngeLqw

https://llimllib.github.io/bloomfilter-tutorial/

Sorted String Table : SStable

 https://www.igvita.com/2012/02/06/sstable-and-log-structured-storage-leveldb/

Linux shell programming

 - without permission change

/bin/sh <name of script>

- make scrhipt to be an excutable file

chmod +x <name of script>

sar : system activity report

on linux

sar : system activity report

Rendering : Glossary

• OpenGL: a formal specification of a graphics API that defines the layout and output of each function.

• GLAD: an extension loading library that loads and sets all OpenGL’s function pointers for us so we can use all (modern) OpenGL’s functions.

• Viewport: the 2D window region where we render to.

• Graphics Pipeline: the entire process vertices have to walk through before ending up

as one or more pixels on the screen.

• Shader: a small program that runs on the graphics card. Several stages of the graphics

pipeline can use user-made shaders to replace existing functionality.

• Vertex: a collection of data that represent a single point.

• Normalized Device Coordinates: the coordinate system your vertices end up in

after perspective division is performed on clip coordinates. All vertex positions in NDC

between -1.0 and 1.0 will not be discarded or clipped and end up visible.

• Vertex Buffer Object: a buffer object that allocates memory on the GPU and stores

all the vertex data there for the graphics card to use.

• Vertex Array Object: stores buffer and vertex attribute state information.

• Element Buffer Object: a buffer object that stores indices on the GPU for indexed

drawing.

• Uniform: a special type of GLSL variable that is global (each shader in a shader program

can access this uniform variable) and only has to be set once.

• Texture: a special type of image used in shaders and usually wrapped around objects,

giving the illusion an object is extremely detailed.

• Texture Wrapping: defines the mode that specifies how OpenGL should sample textures

when texture coordinates are outside the range: (0, 1).

• Texture Filtering: defines the mode that specifies how OpenGL should sample the

texture when there are several texels (texture pixels) to choose from. This usually occurs

when a texture is magnified.

• Mipmaps: stored smaller versions of a texture where the appropriate sized version is chosen based on the distance to the viewer.

• stb_image: image loading library.

• Texture Units: allows for multiple textures on a single shader program by binding

multiple textures, each to a different texture unit.

• Vector: a mathematical entity that defines directions and/or positions in any dimension.

• Matrix: a rectangular array of mathematical expressions with useful transformation properties.

• GLM: a mathematics library tailored for OpenGL.

• Local Space: the space an object begins in. All coordinates relative to an object’s origin.

• World Space: all coordinates relative to a global origin.

• View Space: all coordinates as viewed from a camera’s perspective.

• Clip Space: all coordinates as viewed from the camera’s perspective but with projection

applied. This is the space the vertex coordinates should end up in, as output of the vertex

108 Chapter 11. Review shader. OpenGL does the rest (clipping/perspective division).

• Screen Space: all coordinates as viewed from the screen. Coordinates range from 0 to

screen width/height.

• LookAt: a special type of view matrix that creates a coordinate system where all coordinates are rotated and translated in such a way that the user is looking at a given target from a given position.

• Euler Angles: defined as yaw, pitch and roll that allow us to form any 3D direction

vector from these 3 values.