Lightning with some light points

Lightning with some light points

Brunocogo

Member #16,393

June 2016

Hey guys, i'm studying allegro library, and i'm trying to create a game. i want to put in my game, a light effect, and i got, but i also want a light points arround the map like this:
https://www.youtube.com/watch?v=_YVTOaUKO0Q

but when i come to the light point, happens it:

https://postimg.org/image/op1hpw6dd/

i'm doing that with blends, but i dont know how to proceed, anyone can help me? AHAH

part of code:

darkarea = al_create_bitmap(SCREEN_W, SCREEN_H);
al_set_target_bitmap(darkarea);

al_set_blender(ALLEGRO_ADD , ALLEGRO_ONE , ALLEGRO_ZERO);
al_clear_to_color(al_map_rgba_f(0, 0, 0,0.9));

al_draw_bitmap(light2, 1000-camera_x, 1000-camera_y , 0); // light point
al_draw_bitmap(light, 275, 170 , 0); //light that follow player

al_set_blender(ALLEGRO_ADD, ALLEGRO_ONE, ALLEGRO_INVERSE_ALPHA);
al_set_target_backbuffer(display);

al_draw_bitmap(darkarea, 0, 0, NULL);

al_destroy_bitmap(darkarea);

bamccaig

Member #7,536

July 2006

I'm completely clueless about any of the GL language stuff and shaders and the like, but the obvious thing occurs to me: are you drawing things in an appropriate order? I'm not sure how your lighting is being handled, but I could imagine that the bitmap that is not lighted was drawn over top of the rest.

--
I mean the best with what I say. It doesn't always sound that way.

Mark Oates

Member #1,146

March 2001

I would do it like this:

#SelectExpand
  1#include <iostream>
  2#include <vector>
  3
  4
  5class LightMask
  6{
  7private:
 class point2d
 {
 public:
    float x;
    float y;
    point2d(float x, float y) : x(x), y(y) {}
 };
 15
 ALLEGRO_BITMAP *surface;
 ALLEGRO_BITMAP *light_bitmap;
 std::vector<point2d> points;
 19
 void update_surface()
 {
    ALLEGRO_STATE previous_state;
    al_store_state(&previous_state, ALLEGRO_STATE_TARGET_BITMAP | ALLEGRO_STATE_BLENDER);
    al_set_target_bitmap(surface);
    al_clear_to_color(al_map_rgb(0, 0, 0));
    al_set_blender(ALLEGRO_ADD, ALLEGRO_ONE, ALLEGRO_ONE);
 27
    for (auto &point : points)
    {
       float half_w = al_get_bitmap_width(light_bitmap) * 0.5;
       float half_h = al_get_bitmap_height(light_bitmap) * 0.5;
       al_draw_bitmap(light_bitmap, point.x - half_w, point.y - half_h, 0);
    }
 34
    al_restore_state(&previous_state);
 }
 37
 38public:
 LightMask(int width, int height)
    : surface(al_create_bitmap(width, height))
    , light_bitmap(al_load_bitmap("data/bitmaps/gradient.jpg"))
 {
    if (!light_bitmap) std::cout << "There was an error loading the light bitmap" << std::endl;
 }
 45
 ~LightMask()
 {
    al_destroy_bitmap(surface);
    al_destroy_bitmap(light_bitmap);
 }
 51
 void clear_points()
 {
    points.clear();
 }
 56
 void add_point(float x, float y)
 {
    points.push_back(point2d(x, y));
 }
 61
 void draw()
 {
    update_surface();
 65
    ALLEGRO_STATE previous_state;
    al_store_state(&previous_state, ALLEGRO_STATE_BLENDER);
    al_set_blender(ALLEGRO_ADD, ALLEGRO_DST_COLOR, ALLEGRO_ZERO);
 69
    al_draw_bitmap(surface, 0, 0, 0);
 71
    al_restore_state(&previous_state);
 }
 74};

This object has a very simple API:

LightMask(int w, int h) - create a new lightmask.
void add_point(int x, int y) - adds a light point to your mask.
void clear_points() - removes all the light points from the mask.
void draw() - draws the mask.

Here is the light mask being drawn on a green background. It has two static points, and another point that follows the mouse (click for gif):

{"name":"610432","src":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/4\/6\/4685ce30f58324f61f7186f933af907d.gif","w":656,"h":392,"tn":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/4\/6\/4685ce30f58324f61f7186f933af907d"}

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Brunocogo

Member #16,393

June 2016

can you send me the gradient.jpg please?

Mark Oates

Member #1,146

March 2001

You bet! It's actually attached in my previous post. (paper-clip icon)

--
Visit CLUBCATT.com for cat shirts, cat mugs, puzzles, art and more <-- coupon code ALLEGRO4LIFE at checkout and get $3 off any order of 3 or more items!

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Brunocogo

Member #16,393

June 2016

thanxx man, its work, my problem was the picture. i replaced my picture by your and worked perfectly =D, sorry for my english, i'm a brazilian student and i'm still improving my english AHAHAH