GLSnow.cc

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#include "GLSnow.hh"
#include "Display.hh"
#include "openmsx.hh"
#include <cstdlib>

namespace openmsx {

GLSnow::GLSnow(Display& display_, unsigned width_, unsigned height_)
        : Layer(COVER_FULL, Z_BACKGROUND)
        , display(display_)
        , width(width_), height(height_)
{
        // Create noise texture.
        byte buf[128 * 128];
        for (int i = 0; i < 128 * 128; ++i) {
                buf[i] = byte(rand());
        }
        glGenTextures(1, &noiseTextureId);
        glBindTexture(GL_TEXTURE_2D, noiseTextureId);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE8, 128, 128, 0,
                     GL_LUMINANCE, GL_UNSIGNED_BYTE, buf);
}

GLSnow::~GLSnow()
{
        // Free texture.
        glDeleteTextures(1, &noiseTextureId);
}

void GLSnow::paint(OutputSurface& /*output*/)
{
        // Rotate and mirror noise texture in consecutive frames to avoid
        // seeing 'patterns' in the noise.
        static const int coord[8][4][2] = {
                { { 0, 0 }, { 1, 0 }, { 1, 1 }, { 0, 1 } },
                { { 0, 1 }, { 1, 1 }, { 1, 0 }, { 0, 0 } },
                { { 0, 1 }, { 0, 0 }, { 1, 0 }, { 1, 1 } },
                { { 1, 1 }, { 1, 0 }, { 0, 0 }, { 0, 1 } },
                { { 1, 1 }, { 0, 1 }, { 0, 0 }, { 1, 0 } },
                { { 1, 0 }, { 0, 0 }, { 0, 1 }, { 1, 1 } },
                { { 1, 0 }, { 1, 1 }, { 0, 1 }, { 0, 0 } },
                { { 0, 0 }, { 0, 1 }, { 1, 1 }, { 1, 0 } }
        };
        static unsigned cnt = 0;

        // Draw noise texture.
        GLfloat x = GLfloat(rand()) / RAND_MAX;
        GLfloat y = GLfloat(rand()) / RAND_MAX;
        cnt = (cnt + 1) % 8;
        glEnable(GL_TEXTURE_2D);
        glBindTexture(GL_TEXTURE_2D, noiseTextureId);
        glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
        glBegin(GL_QUADS);
        glTexCoord2f(0.0f + x, 2.0f + y);
        glVertex2i(coord[cnt][0][0] * width, coord[cnt][0][1] * height);
        glTexCoord2f(2.0f + x, 2.0f + y);
        glVertex2i(coord[cnt][1][0] * width, coord[cnt][1][1] * height);
        glTexCoord2f(2.0f + x, 0.0f + y);
        glVertex2i(coord[cnt][2][0] * width, coord[cnt][2][1] * height);
        glTexCoord2f(0.0f + x, 0.0f + y);
        glVertex2i(coord[cnt][3][0] * width, coord[cnt][3][1] * height);
        glEnd();
        glDisable(GL_TEXTURE_2D);

        display.repaintDelayed(100 * 1000); // 10fps
}

} // namespace openmsx