Justin Fletcher

Author: Justin Fletcher

[tldr: code at bottom]

Let me explain the title. I wanted to have a UITableView that adds new rows, and also scrolls to the new row that just got inserted.

But theres the annoying that if you’re viewing older rows in the middle of the tableview, you don’t want the tableview to scroll you away from that when it adds a new row.

I created this method that only scrolls to the newly added row, when you’re at the end of the tableview, so if you’re viewing some data in the middle of the tableview, it won’t scroll you away from it. This works with both single-section and multi-section tableviews as well. Explanation in the code comments. It’s pretty simple actually.

It’s also useful for anyone looking for how to make the table scroll when adding a new row, regardless of where you are in the tableview.

Enjoy, this is coming straight from a new game project I’m working on.

-(void)addRowAndScrollWithIndexPath:(NSIndexPath*)path {
    
    //check if the last viewable index path is one less than the path being
    //added. this way we know we're at the bottom.
    
    //array of visible paths.
    NSArray *visiblePaths = [table indexPathsForVisibleRows];
    
    //last visible object's index path.
    NSIndexPath *bottomPath = [visiblePaths lastObject];
    
    //row and section of last visible row.
    NSInteger bRow = [bottomPath row];
    NSInteger bSection = [bottomPath section];
    //row and section or row in parameter.
    NSInteger row = [path row];
    NSInteger section = [path section];
    
    /*
     so it should only scroll if you're viewing the index path previous to the
     path specified in the parameter. (only possible if their sections are equal AND
     the parameter row is one more than the last visible row), OR
     (the section of the parameter is one more than the last visible row
     AND the row of the parameter is 0), meaning its the first in a new section.
     */
    //first condition.
    BOOL nextRowInSameSection = (section == bSection) && (row == (bRow+1));
    //second condition.
    BOOL firstRowInNextSection = ((section == (bSection+1)) && (row == 0));
    
    //one or the other.
    BOOL shouldScroll = nextRowInSameSection || firstRowInNextSection;
    
    //array of indexPaths to add.
    NSArray *indexPaths = [NSArray arrayWithObject:path];
    
    //add the row to the table view.
    [table insertRowsAtIndexPaths:indexPaths withRowAnimation:UITableViewRowAnimationFade];
    
    //if you should scroll based on the booleans above.. do so to the new path.
    if (shouldScroll) {
        [table scrollToRowAtIndexPath:path atScrollPosition:UITableViewScrollPositionBottom animated:YES];
    }
}

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-(void)addRowAndScrollWithIndexPath:(NSIndexPath*)path {

//check if the last viewable index path is one less than the path being

//added. this way we know we're at the bottom.

//array of visible paths.

NSArray *visiblePaths = [table indexPathsForVisibleRows];

//last visible object's index path.

NSIndexPath *bottomPath = [visiblePaths lastObject];

//row and section of last visible row.

NSInteger bRow = [bottomPath row];

NSInteger bSection = [bottomPath section];

//row and section or row in parameter.

NSInteger row = [path row];

NSInteger section = [path section];

/*

so it should only scroll if you're viewing the index path previous to the

path specified in the parameter. (only possible if their sections are equal AND

the parameter row is one more than the last visible row), OR

(the section of the parameter is one more than the last visible row

AND the row of the parameter is 0), meaning its the first in a new section.

*/

//first condition.

BOOL nextRowInSameSection = (section == bSection) && (row == (bRow+1));

//second condition.

BOOL firstRowInNextSection = ((section == (bSection+1)) && (row == 0));

//one or the other.

BOOL shouldScroll = nextRowInSameSection || firstRowInNextSection;

//array of indexPaths to add.

NSArray *indexPaths = [NSArray arrayWithObject:path];

//add the row to the table view.

[table insertRowsAtIndexPaths:indexPaths withRowAnimation:UITableViewRowAnimationFade];

//if you should scroll based on the booleans above.. do so to the new path.

if (shouldScroll) {

[table scrollToRowAtIndexPath:path atScrollPosition:UITableViewScrollPositionBottom animated:YES];

}

As always, comments and questions are welcome.

Author: Justin Fletcher

Category : Full Script , Shader , Unity

Here’s a great shader I found for giving a material scanlines. It creates a very cool retro tv effect. Forgive me I don’t have a source link, I couldn’t find it again. So a special thanks to whoever did write it, if you’re out there, leave a comment or if anyone finds the original link, it was part of a Unity Answers thread, post a comment. Anyway, here’s the shader, use it, enjoy!

Shader "Custom/Scanlines" { 
Properties { 
    _Color("Color", Color) = (0,0,0,1) 
    _LinesSize("LinesSize", Range(1,10)) = 1 
} 
SubShader { 
    Tags {"IgnoreProjector" = "True" "Queue" = "Overlay"} 
    Fog { Mode Off } 
    Pass { 
        ZTest Always 
        ZWrite Off 
        Blend SrcAlpha OneMinusSrcAlpha

CGPROGRAM
 
#pragma vertex vert 
#pragma fragment frag
#include "UnityCG.cginc"

        fixed4 _Color; half _LinesSize;

        struct v2f { 
            half4 pos:POSITION; 
            fixed4 sPos:TEXCOORD; 
        };

        v2f vert(appdata_base v) {
            v2f o; o.pos = mul(UNITY_MATRIX_MVP, v.vertex); 
            o.sPos = ComputeScreenPos(o.pos); 
            return o; 
        }

        fixed4 frag(v2f i) : COLOR {
            fixed p = i.sPos.y / i.sPos.w;

            if((int)(p*_ScreenParams.y/floor(_LinesSize))%2==0) discard;

               return _Color; 
         }
 
ENDCG
       }

} 

}

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Shader "Custom/Scanlines" {

Properties {

_Color("Color", Color) = (0,0,0,1)

_LinesSize("LinesSize", Range(1,10)) = 1

}

SubShader {

Tags {"IgnoreProjector" = "True" "Queue" = "Overlay"}

Fog { Mode Off }

Pass {

ZTest Always

ZWrite Off

Blend SrcAlpha OneMinusSrcAlpha

CGPROGRAM

#pragma vertex vert

#pragma fragment frag

#include "UnityCG.cginc"

fixed4 _Color; half _LinesSize;

struct v2f {

half4 pos:POSITION;

fixed4 sPos:TEXCOORD;

};

v2f vert(appdata_base v) {

v2f o; o.pos = mul(UNITY_MATRIX_MVP, v.vertex);

o.sPos = ComputeScreenPos(o.pos);

return o;

}

fixed4 frag(v2f i) : COLOR {

fixed p = i.sPos.y / i.sPos.w;

if((int)(p*_ScreenParams.y/floor(_LinesSize))%2==0) discard;

return _Color;

}

ENDCG

}

Author: Justin Fletcher

Category : Full Script , Shader , Unity

Here’s a shader we wrote to add the color property to the Unity Alpha Blended Shader under Mobile/Particles/Alpha Blended.

Shader "Mobile/Particles/Alpha Blended Color" {
    Properties {
        _Color ("Color", Color) = (1,1,1,1)
        _MainTex ("Particle Texture", 2D) = "white" {}
    }
    
    Category {
        
        Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" }
        Blend SrcAlpha OneMinusSrcAlpha
        Cull Back Lighting Off ZWrite Off
        
        BindChannels {
            Bind "Color", color
            Bind "Vertex", vertex
            Bind "TexCoord", texcoord
        }
        
        SubShader {        
            Pass {
                SetTexture[_MainTex] {
                    ConstantColor [_Color]
                    Combine Texture * constant
                }
            }
        }
    }    
    
}

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Shader "Mobile/Particles/Alpha Blended Color" {

Properties {

_Color ("Color", Color) = (1,1,1,1)

_MainTex ("Particle Texture", 2D) = "white" {}

}

Category {

Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" }

Blend SrcAlpha OneMinusSrcAlpha

Cull Back Lighting Off ZWrite Off

BindChannels {

Bind "Color", color

Bind "Vertex", vertex

Bind "TexCoord", texcoord

}

SubShader {

Pass {

SetTexture[_MainTex] {

ConstantColor [_Color]

Combine Texture * constant

}

Author: Justin Fletcher

Category : C# , Full Script , Game Development , Unity

Great little script for Unity that makes a LineRenderer component shape into a circle or ellipse, given the number of line segments along with x and y radius.

Script by MarkPixel. Original thread here. Full Script Below.

Author: Justin Fletcher

Category : Full Script , Game Development , Javascript , Unity

Earlier today I stumbled upon a perfect little script for extracting audio data from an audiosource component in unity. It does all the calculation for getting the RMS value, the decibels, and frequency.

This script can easily be applied to make things behave to the music being played in the Audiosource component. Like making an object bounce or move back and forth with the music.

Thanks to Aldonaletto from this Unity Answers post for making this one and explaining it so well. Script below.

Author: Justin Fletcher

Category : 2D , 3D , Game Dev Primer , Sine Waves , Trigonometry

If you didn’t read part 1, and want to get background on sine waves for game development. Click Here (PART 1).

If you did read it, or don’t care, please continue.

Last time it was all about the basic sine function and how to make game objects move in the shape of a sine wave. This time let’s take it a step further. I’m going to show you a few more practical applications of sine waves, that isn’t limited to just moving objects.

Oscillations

I think I used the word oscillate more than 6 times in the last post, but it’s the essence of sine waves. This post isn’t going to be too long, since I think you’ll catch on quick if you haven’t already. Basically what I’m telling you, is that if you want anything to smoothly move back and forth (oscillate) between two states, values, locations, etc, USE THE SINE FUNCTION.

Author: Justin Fletcher

Category : 2D , 2D Movement , Game Dev Primer , Game Development , Sine Waves , Trigonometry

Don’t worry, this isn’t going to be a whole Trig class. I will however, go over one very useful trigonometric function that is easily overlooked by beginner, and even veteran game developers. The Sine Wave. Hopefully this will fuel your own curiosity to learn more about trigonometry and how applicable it is to the world of game development.

If you know what the Sine function is, fantastic, if not, I’m sure you’ve heard the term. You may have encountered it in high school geometry or trigonometry, and it’s applied in just about every field that involves some kind of math.

Sine waves are a graph of the Sine function, and given a basic form, as the input value changes, the output will oscillate between 1 and -1. Here’s what that looks like:

Note: You may notice that the sine wave perfectly maps to a circle of radius 1. That form of circle is called a Unit Circle. Understanding it is helpful but not necessary. As I said this is not a trig class. Moving on.

Author: Justin Fletcher

Category : 2D , C# , Full Script , Game Development , Unity

While working in Unity I found it difficult to figure out how to get an object to rotate. If you’re reading this, you probably did too. Right now I’m just talking about 2D game object rotation. The concept works in 3D as well, just turn on a different axis, but I won’t go into that here.

If you don’t feel like reading the article and just want the Full Script… skip to the bottom.

Add this to the property section of your class:

public float degreesPerSec = 360f;

1	public float degreesPerSec = 360f;

This will be the variable that tells the script how fast to rotate around the axis. It’s in degrees per second. Feel free to play with the number as see how it affects the rotation speed.