[vlc-devel] [PATCH 24/27] doc: opengl filter: add triangle sample

Romain Vimont rom1v at videolabs.io
Thu Jun 25 14:23:11 CEST 2020


Co-authored-by: Alexandre Janniaux <ajanni at videolabs.io>
---
 doc/opengl_filters/Makefile.am |   7 ++
 doc/opengl_filters/triangle.c  | 197 +++++++++++++++++++++++++++++++++
 2 files changed, 204 insertions(+)
 create mode 100644 doc/opengl_filters/triangle.c

diff --git a/doc/opengl_filters/Makefile.am b/doc/opengl_filters/Makefile.am
index b43431a2d3..ca1f49a5a6 100644
--- a/doc/opengl_filters/Makefile.am
+++ b/doc/opengl_filters/Makefile.am
@@ -23,6 +23,13 @@ OPENGL_FILTERS =
 
 if WANT_OPENGL_FILTERS_SAMPLES
 # filters enabled only when configured with --enable-opengl-filters-samples
+
+OPENGL_FILTERS += libglfilter_triangle_plugin.la
+libglfilter_triangle_plugin_la_SOURCES = opengl_filters/triangle.c
+libglfilter_triangle_plugin_la_CFLAGS = $(OPENGL_FILTERS_CFLAGS)
+libglfilter_triangle_plugin_la_LIBADD = $(LTLIBVLCCORE) $(LTLIBVLCGL)
+libglfilter_triangle_plugin_la_LDFLAGS = $(OPENGL_FILTERS_LDFLAGS)
+
 endif
 
 lib_LTLIBRARIES = $(OPENGL_FILTERS)
diff --git a/doc/opengl_filters/triangle.c b/doc/opengl_filters/triangle.c
new file mode 100644
index 0000000000..44860dbe9d
--- /dev/null
+++ b/doc/opengl_filters/triangle.c
@@ -0,0 +1,197 @@
+/*****************************************************************************
+ * triangle.c
+ *****************************************************************************
+ * Copyright (C) 2020 VLC authors and VideoLAN
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include <assert.h>
+
+#include <vlc_common.h>
+#include <vlc_plugin.h>
+#include <vlc_modules.h>
+#include <vlc_opengl.h>
+
+#include "filter.h"
+#include "gl_api.h"
+#include "gl_common.h"
+#include "gl_util.h"
+
+struct sys {
+    GLuint program_id;
+
+    GLuint vbo;
+
+    struct {
+        GLint vertex_pos;
+        GLint vertex_color;
+    } loc;
+};
+
+static int
+Draw(struct vlc_gl_filter *filter, const struct vlc_gl_input_meta *meta)
+{
+    (void) meta;
+
+    struct sys *sys = filter->sys;
+
+    const opengl_vtable_t *vt = &filter->api->vt;
+
+    vt->UseProgram(sys->program_id);
+
+    vt->Enable(GL_BLEND);
+    vt->BlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+
+    /*
+     * The VBO data contains, for each vertex, 2 floats for the vertex position
+     * followed by 3 floats for the associated color:
+     *
+     *  |     vertex 0      |     vertex 1      | ...
+     *  | x | y | R | G | B | x | y | R | G | B | x | ...
+     *   \-----/ \---------/
+     * vertex_pos vertex_color
+     */
+
+    const GLsizei stride = 5 * sizeof(float);
+
+    vt->BindBuffer(GL_ARRAY_BUFFER, sys->vbo);
+
+    vt->EnableVertexAttribArray(sys->loc.vertex_pos);
+    vt->VertexAttribPointer(sys->loc.vertex_pos, 2, GL_FLOAT, GL_FALSE, stride,
+                            (const void *) 0);
+
+    intptr_t offset = 2 * sizeof(float);
+    vt->EnableVertexAttribArray(sys->loc.vertex_color);
+    vt->VertexAttribPointer(sys->loc.vertex_color, 3, GL_FLOAT, GL_FALSE,
+                            stride, (const void *) offset);
+
+    vt->DrawArrays(GL_TRIANGLES, 0, 3);
+
+    vt->Disable(GL_BLEND);
+
+    return VLC_SUCCESS;
+}
+
+static void
+Close(struct vlc_gl_filter *filter)
+{
+    struct sys *sys = filter->sys;
+
+    const opengl_vtable_t *vt = &filter->api->vt;
+    vt->DeleteProgram(sys->program_id);
+    vt->DeleteBuffers(1, &sys->vbo);
+
+    free(sys);
+}
+
+static vlc_gl_filter_open_fn Open;
+static int
+Open(struct vlc_gl_filter *filter, const config_chain_t *config,
+     struct vlc_gl_tex_size *size_out)
+{
+    (void) config;
+    (void) size_out;
+
+    struct sys *sys = filter->sys = malloc(sizeof(*sys));
+    if (!sys)
+        return VLC_EGENERIC;
+
+#ifdef USE_OPENGL_ES2
+# define SHADER_VERSION "#version 100\n"
+# define FRAGMENT_SHADER_PRECISION "precision highp float;\n"
+#else
+# define SHADER_VERSION "#version 120\n"
+# define FRAGMENT_SHADER_PRECISION
+#endif
+
+    static const char *const VERTEX_SHADER =
+        SHADER_VERSION
+        "attribute vec2 vertex_pos;\n"
+        "attribute vec3 vertex_color;\n"
+        "varying vec3 color;\n"
+        "void main() {\n"
+        "  gl_Position = vec4(vertex_pos, 0.0, 1.0);\n"
+        "  color = vertex_color;\n"
+        "}\n";
+
+    static const char *const FRAGMENT_SHADER =
+        SHADER_VERSION
+        FRAGMENT_SHADER_PRECISION
+        "varying vec3 color;\n"
+        "void main() {\n"
+        "  gl_FragColor = vec4(color, 0.5);\n"
+        "}\n";
+
+    const opengl_vtable_t *vt = &filter->api->vt;
+
+    GLuint program_id =
+        vlc_gl_BuildProgram(VLC_OBJECT(filter), vt,
+                            1, (const char **) &VERTEX_SHADER,
+                            1, (const char **) &FRAGMENT_SHADER);
+
+    if (!program_id)
+        goto error;
+
+    sys->program_id = program_id;
+
+    sys->loc.vertex_pos = vt->GetAttribLocation(program_id, "vertex_pos");
+    assert(sys->loc.vertex_pos != -1);
+
+    sys->loc.vertex_color = vt->GetAttribLocation(program_id, "vertex_color");
+    assert(sys->loc.vertex_color != -1);
+
+    vt->GenBuffers(1, &sys->vbo);
+
+    static const GLfloat data[] = {
+      /* x   y      R  G  B */
+         0,  1,     1, 0, 0,
+        -1, -1,     0, 1, 0,
+         1, -1,     0, 0, 1,
+    };
+
+    vt->BindBuffer(GL_ARRAY_BUFFER, sys->vbo);
+    vt->BufferData(GL_ARRAY_BUFFER, sizeof(data), data, GL_STATIC_DRAW);
+    vt->BindBuffer(GL_ARRAY_BUFFER, 0);
+
+    filter->config.blend = true;
+    filter->config.msaa_level = 4;
+
+    static const struct vlc_gl_filter_ops ops = {
+        .draw = Draw,
+        .close = Close,
+    };
+    filter->ops = &ops;
+
+    return VLC_SUCCESS;
+
+error:
+    free(sys);
+    return VLC_EGENERIC;
+}
+
+vlc_module_begin()
+    set_shortname("triangle")
+    set_description("OpenGL triangle blender")
+    set_category(CAT_VIDEO)
+    set_subcategory(SUBCAT_VIDEO_VFILTER)
+    set_capability("opengl filter", 0)
+    set_callback(Open)
+    add_shortcut("triangle")
+vlc_module_end()
-- 
2.27.0



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