Trying to implement a shockwave shader using sf::Shader

[Sumzary]

This is the shockwave.frag file:

uniform sampler2D in_Texture; // 0
uniform vec2 in_Center; // Mouse position
uniform float in_Time; // effect elapsed time. Multiply this to affect speed.

// Amplitude?, Refraction?, Width? e.g. 10.0, 0.8, 0.1
uniform vec3 in_ShockParams;

uniform int in_WindowWidth;
uniform int in_WindowHeight;

varying vec2 var_TexCoord;

void main()
{
  vec2 uv = var_TexCoord;
  vec2 texCoord = uv;
  float x = in_Center.x / float(in_WindowWidth);
  float y = (float(in_WindowHeight) - in_Center.y) / float(in_WindowHeight);
  float distance = distance(uv, vec2(x, y));

  if ( (distance <= (in_Time + in_ShockParams.z)) &&
       (distance >= (in_Time - in_ShockParams.z)) )
  {
    float diff = (distance - in_Time);
    float powDiff = 1.0 - pow(abs(diff * in_ShockParams.x),
                                in_ShockParams.y);
    float diffTime = diff * powDiff;
    vec2 diffUV = normalize(uv - in_Center);
    texCoord = uv + (diffUV * diffTime);
  }

  gl_FragColor = texture2D(in_Texture, texCoord);
}

This is all the relevant code:

shader.loadFromFile("Vania/Shaders/shockwave.frag", sf::Shader::Fragment);
shader.setParameter("in_Center", 0.5f, 0.5f);
shader.setParameter("in_ShockParams", 10.f, 0.8f, 0.1f);
shader.setParameter("in_Time", 2.f);
shader.setParameter("in_WindowWidth", conf::res.x);
shader.setParameter("in_WindowHeight", conf::res.y);

...

window.draw(renderSprite, &shader);

Everything seems fine so far, but when i start the game, all I see is one solid color (would put screenshot here but it seems pointless), is there something wrong with my SFML code? Something obvious I'm missing here? Been stuck for a while trying to figure this out, some help would be very much appreciated ;]

[eXpl0it3r]

You never clear or display the drawn thing - at least you didn't post it. Please provide a complete and minimal example, so we can directly test it.

[Laurent]

You should start with a minimal shader and build on top of it until things stop working as expected. Writing the final thing directly and then wondering why it doesn't work often leads nowhere

And where do you set the in_Texture parameter? It's not shown in your code.

[Sumzary]

Here you go lad

#include <SFML/System.hpp>
#include <SFML/Graphics.hpp>
#include <SFML/Window.hpp>


int main() {

        sf::RenderWindow window(sf::VideoMode(640, 360), "Test 123");

        sf::RenderTexture texture;
        texture.create(640, 360);

        sf::Texture tex;
        tex.loadFromFile("Image.png");

        sf::Sprite sprite;
        sprite.setTexture(tex);

        sf::Shader shader;
        shader.loadFromFile("Shockwave.frag", sf::Shader::Fragment);
        shader.setParameter("in_Center", 0.5f, 0.5f);
        shader.setParameter("in_ShockParams", 10.f, 0.8f, 0.1f);
        shader.setParameter("in_Time", 1.f);
        shader.setParameter("in_WindowWidth", 640);
        shader.setParameter("in_WindowHeight", 360);

        // The main loop
        while (window.isOpen()) {

                // Event processing
                sf::Event event;
                while (window.pollEvent(event)) {

                        if (event.type == sf::Event::Closed)
                                window.close();
                }

                texture.clear(sf::Color::Red);
                texture.draw(sprite);
                texture.display();

                sf::Sprite rSprite(texture.getTexture());

                window.clear();
                window.draw(rSprite, &shader);
                window.display();
        }
}
 

Just have a random image around and copy the shader stuff to a file.

EDIT: Didn't actually write this myself, found it on the internet, thats why I'm struggling so much :|

[cob59]

About shaders, I came across this topic once. It might help :
http://gmc.yoyogames.com/index.php?showtopic=586380

[G.]

var_TexCoord has no value. It's probably initialized in a vertex shader in the code you blindly copied. :p
Also, what Laurent asked.

[Sumzary]

After some googling and testing this is what I got.

The C++ code in "main.cpp":

#include <SFML/System.hpp>
#include <SFML/Graphics.hpp>
#include <SFML/Window.hpp>


int main() {

        sf::RenderWindow window(sf::VideoMode(640, 360), "Test 123");

        sf::RenderTexture texture;
        texture.create(640, 360);

        sf::Texture tex;
        tex.loadFromFile("Image.png");

        sf::Sprite sprite;
        sprite.setTexture(tex);

        sf::Shader shader;
        shader.loadFromFile("Shockwave.vert", "Shockwave.frag");
        shader.setParameter("in_Texture", sf::Shader::CurrentTexture);
        shader.setParameter("in_Center", 0.5f, 0.5f);
        shader.setParameter("in_ShockParams", 10.0f, 0.8f, 0.1f);
        shader.setParameter("in_WindowWidth", 640);
        shader.setParameter("in_WindowHeight", 360);

        sf::Clock clock;
        clock.restart();

        // The main loop
        while (window.isOpen()) {

                // Event processing
                sf::Event event;
                while (window.pollEvent(event)) {

                        if (event.type == sf::Event::Closed)
                                window.close();
                }

                shader.setParameter("in_Time", clock.getElapsedTime().asSeconds());

                texture.clear(sf::Color::Red);
                texture.draw(sprite);
                texture.display();

                sf::Sprite rSprite(texture.getTexture());

                window.clear();
                window.draw(rSprite, &shader);
                window.display();
        }
}
 

The "Shockwave.vert":

#version 110

attribute vec4 in_Color;

varying vec4 var_Color;
varying vec2 var_TexCoord;

void main()
{
  gl_Position = ftransform();
  var_Color = in_Color;
  var_TexCoord = gl_MultiTexCoord0.xy;
}

And the "Shockwave.frag":

#version 110

uniform sampler2D in_Texture; // 0
uniform vec2 in_Center; // Mouse position
uniform float in_Time; // effect elapsed time. Multiply this to affect speed.

// Amplitude?, Refraction?, Width? e.g. 10.0, 0.8, 0.1
uniform vec3 in_ShockParams;

uniform int in_WindowWidth;
uniform int in_WindowHeight;

varying vec2 var_TexCoord;

void main()
{
  vec2 uv = var_TexCoord;
  vec2 texCoord = uv;
  float x = in_Center.x / float(in_WindowWidth);
  float y = (float(in_WindowHeight) - in_Center.y) / float(in_WindowHeight);
  float distance = distance(uv, vec2(x, y));

  if ( (distance <= (in_Time + in_ShockParams.z)) &&
       (distance >= (in_Time - in_ShockParams.z)) )
  {
    float diff = (distance - in_Time);
    float powDiff = 1.0 - pow(abs(diff * in_ShockParams.x),
                                in_ShockParams.y);
    float diffTime = diff * powDiff;
    vec2 diffUV = normalize(uv - in_Center);
    texCoord = uv + (diffUV * diffTime);
  }

  gl_FragColor = texture2D(in_Texture, texCoord);
}

The program without the shader:


With shader:



It seems to just show this one pixel from the top-left corner, it's like I'm missing something very simple. Ideas?

[the_mean_marine]

You've made a small mistake in your vertex shader.

The line:

var_TexCoord = gl_MultiTexCoord0.xy;

should be:

var_TexCoord = gl_TextureMatrix[0] * gl_MultiTexCoord0;

[Sumzary]

It draws the background image fine, but the effect is just not there, fiddling with different values didn't help. 

[Sumzary]

Actually, I'm getting some errors:

An internal OpenGL call failed in Shader.cpp (235) : GL_INVALID_OPERATION, the specified operation is not allowed in the current state
An internal OpenGL call failed in Shader.cpp (235) : GL_INVALID_OPERATION, the specified operation is not allowed in the current state

Help meh, i'm stumped

[Sumzary]

Well I solved it, these variables were ints:

uniform int in_WindowWidth;
uniform int in_WindowHeight;

Turns out you cant "shader.setParamater(int);", so I had to change the code to make them floats instead:

uniform float in_WindowWidth;
uniform float in_WindowHeight;

A feature to be added mayhaps? 

[Sqasher]

You convert the int to float in the shockwave fragment shader anyway:

float x = in_Center.x / float(in_WindowWidth);
float y = (float(in_WindowHeight) - in_Center.y) / float(in_WindowHeight);
 

Also, graphics cards are made specifically for floating point calculations and can be slow in integer calculations. So I think this won't be added to SFML.