build visualisation for lookAt and projection
This commit is contained in:
parent
daa584842c
commit
525a5a90ad
313
src/main.c
313
src/main.c
|
|
@ -15,17 +15,27 @@
|
|||
#define STATUS_INTERVAL 0.5
|
||||
#define PI 3.14159f
|
||||
|
||||
GLFWwindow* window;
|
||||
|
||||
GLuint program;
|
||||
GLuint originProgram;
|
||||
GLuint floorProgram;
|
||||
|
||||
GLuint vertexArrayObject;
|
||||
|
||||
GLuint originVAO;
|
||||
|
||||
GLuint indexBuffer;
|
||||
GLuint lineIndexBuffer;
|
||||
GLuint floorIndexBuffer;
|
||||
|
||||
GLuint initialWindowWidth = 800;
|
||||
GLuint initialWindowHeight = 600;
|
||||
|
||||
GLfloat aspect;
|
||||
mat4 projectionMatrix;
|
||||
mat4 realProjectionMatrix;
|
||||
|
||||
GLfloat currentHue = 0.0f;
|
||||
|
||||
int frameCount = 0;
|
||||
struct timespec last_time, current_time;
|
||||
|
|
@ -77,19 +87,19 @@ void updateStatusDisplay() {
|
|||
double fps = frameCount / elapsed;
|
||||
frameCount = 0;
|
||||
last_time = current_time;
|
||||
printf("\rFPS: %.2f ", fps);
|
||||
printf("\rFPS: %5.2f - currentValue: %5.2f", fps, currentHue);
|
||||
fflush(stdout);
|
||||
}
|
||||
}
|
||||
|
||||
void recalculateProjectionMatrix() {
|
||||
mat4BuildPerspective(projectionMatrix, 60 * M_PI / 180, aspect, 0.1, 10);
|
||||
mat4BuildPerspective(realProjectionMatrix, 90 * M_PI / 180, aspect, 0.1, 50);
|
||||
DEBUG("Recalculating Projection Matrix");
|
||||
}
|
||||
|
||||
void init(void) {
|
||||
|
||||
INFO("Building Programs...");
|
||||
INFO("Building main program...");
|
||||
ProgramLinkResult linkResult = buildShaderProgram("src/shaders/vertex.glsl", "src/shaders/fragment.glsl");
|
||||
if (!linkResult.success) {
|
||||
FATAL("Failed to link Program");
|
||||
|
|
@ -98,6 +108,25 @@ void init(void) {
|
|||
|
||||
program = linkResult.program;
|
||||
|
||||
|
||||
INFO("Building origin program...");
|
||||
linkResult = buildShaderProgram("src/shaders/origin-vertex.glsl", "src/shaders/origin-fragment.glsl");
|
||||
if (!linkResult.success) {
|
||||
FATAL("Failed to link Program");
|
||||
exit(1);
|
||||
}
|
||||
|
||||
originProgram = linkResult.program;
|
||||
|
||||
INFO("Building floor program...");
|
||||
linkResult = buildShaderProgram("src/shaders/floor-vertex.glsl", "src/shaders/floor-fragment.glsl");
|
||||
if (!linkResult.success) {
|
||||
FATAL("Failed to link Program");
|
||||
exit(1);
|
||||
}
|
||||
|
||||
floorProgram = linkResult.program;
|
||||
|
||||
INFO("Shader Program Done.");
|
||||
|
||||
// create triangle buffer
|
||||
|
|
@ -158,6 +187,32 @@ void init(void) {
|
|||
7, 3, 6
|
||||
};
|
||||
|
||||
GLuint lineIndices[] = {
|
||||
0, 1,
|
||||
0, 2,
|
||||
0, 4,
|
||||
|
||||
1, 3,
|
||||
1, 5,
|
||||
|
||||
2, 3,
|
||||
2, 6,
|
||||
|
||||
3, 7,
|
||||
|
||||
4, 5,
|
||||
4, 6,
|
||||
|
||||
5, 7,
|
||||
|
||||
6, 7
|
||||
};
|
||||
|
||||
GLuint floorIndices[] = {
|
||||
2, 3, 6,
|
||||
3, 7, 6
|
||||
};
|
||||
|
||||
DEBUG("Creating vertext buffer");
|
||||
GLuint vertexBuffer;
|
||||
glGenBuffers(1, &vertexBuffer);
|
||||
|
|
@ -181,24 +236,79 @@ void init(void) {
|
|||
0 // start offset
|
||||
);
|
||||
glEnableVertexAttribArray(0);
|
||||
glVertexAttribPointer(
|
||||
1, // shader location
|
||||
3, // number of values to read
|
||||
GL_FLOAT, // type of value
|
||||
GL_FALSE, // if values are normalised
|
||||
3 * sizeof(GLfloat), // stride - distance between vertices
|
||||
0 // start offset
|
||||
);
|
||||
glEnableVertexAttribArray(1);
|
||||
|
||||
DEBUG("Creating index buffers");
|
||||
|
||||
|
||||
DEBUG("Creating index buffer");
|
||||
glGenBuffers(1, &indexBuffer);
|
||||
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffer);
|
||||
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
|
||||
|
||||
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
|
||||
|
||||
|
||||
|
||||
glGenBuffers(1, &lineIndexBuffer);
|
||||
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, lineIndexBuffer);
|
||||
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(lineIndices), lineIndices, GL_STATIC_DRAW);
|
||||
|
||||
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
|
||||
|
||||
|
||||
|
||||
glGenBuffers(1, &floorIndexBuffer);
|
||||
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, floorIndexBuffer);
|
||||
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(floorIndices), floorIndices, GL_STATIC_DRAW);
|
||||
|
||||
|
||||
glBindBuffer(GL_ARRAY_BUFFER, 0);
|
||||
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
|
||||
glBindVertexArray(0);
|
||||
|
||||
glClearColor(0.0f, 0.0f, 0.0f, 0.3f);
|
||||
|
||||
glClearColor(0.3f, 0.3f, 0.4f, 1.0f);
|
||||
glViewport(0, 0, initialWindowWidth, initialWindowHeight);
|
||||
|
||||
glEnable(GL_CULL_FACE);
|
||||
// glEnable(GL_CULL_FACE);
|
||||
glFrontFace(GL_CCW);
|
||||
|
||||
glEnable(GL_DEPTH_TEST);
|
||||
|
||||
glEnable(GL_BLEND);
|
||||
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
|
||||
|
||||
DEBUG("Creating origin vertex buffer");
|
||||
GLfloat originVertices[] = {
|
||||
// X Y Z R G B
|
||||
0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f,
|
||||
1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f,
|
||||
0.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f,
|
||||
0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f,
|
||||
0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f,
|
||||
0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f
|
||||
};
|
||||
GLuint originVBO;
|
||||
glGenBuffers(1, &originVBO);
|
||||
glBindBuffer(GL_ARRAY_BUFFER, originVBO);
|
||||
glBufferData(GL_ARRAY_BUFFER, sizeof(originVertices), originVertices, GL_STATIC_DRAW);
|
||||
|
||||
glGenVertexArrays(1, &originVAO);
|
||||
glBindVertexArray(originVAO);
|
||||
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), 0);
|
||||
glEnableVertexAttribArray(0);
|
||||
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), (void*)(3 * sizeof(GLfloat)));
|
||||
glEnableVertexAttribArray(1);
|
||||
glBindBuffer(GL_ARRAY_BUFFER, 0);
|
||||
|
||||
initialiseStatusDisplay();
|
||||
|
||||
recalculateProjectionMatrix();
|
||||
|
|
@ -206,15 +316,8 @@ void init(void) {
|
|||
INFO("--- Initialisation done ---");
|
||||
}
|
||||
|
||||
GLfloat currentHue = 0.0f;
|
||||
|
||||
void drawCube(vec3 position, mat4 initialModelMatrix, mat4 viewMatrix) {
|
||||
mat4 modelMatrix;
|
||||
void drawCube(mat4 modelMatrix, mat4 viewMatrix) {
|
||||
mat4 modelViewMatrix;
|
||||
|
||||
mat4Translate(modelMatrix, initialModelMatrix, position);
|
||||
|
||||
// combine model and view matrix to model-view matrix
|
||||
mat4Multiply(modelViewMatrix, viewMatrix, modelMatrix);
|
||||
|
||||
// send modelView and projection matrix to shader
|
||||
|
|
@ -227,54 +330,198 @@ void drawCube(vec3 position, mat4 initialModelMatrix, mat4 viewMatrix) {
|
|||
glDrawElements(GL_TRIANGLES, 48, GL_UNSIGNED_INT, 0);
|
||||
}
|
||||
|
||||
GLfloat clamp(GLfloat d, GLfloat min, GLfloat max) {
|
||||
const GLfloat t = d < min ? min : d;
|
||||
return t > max ? max : t;
|
||||
}
|
||||
|
||||
GLfloat mapTo01(GLfloat d, GLfloat min, GLfloat max) {
|
||||
return (clamp(d, min, max) - min) * (1 / (max - min));
|
||||
}
|
||||
|
||||
void draw(void) {
|
||||
// 0.0: virtual view
|
||||
// 0.1 transition to real view
|
||||
// 0.15 done
|
||||
// 0.3 start view transformation
|
||||
// 0.35 done
|
||||
// 0.4 start projection
|
||||
// 0.45 done
|
||||
updateStatusDisplay();
|
||||
|
||||
mat4 identity;
|
||||
mat4Identity(identity);
|
||||
|
||||
mat4 projectionMatrix;
|
||||
// mat4Interpolate(projectionMatrix, identity, projectionMatrix, mapTo01(currentHue, 0.0f, 0.1f));
|
||||
|
||||
// counter for animation
|
||||
currentHue += 0.0005f;
|
||||
currentHue += 0.0001f;
|
||||
int state = glfwGetKey(window, GLFW_KEY_SPACE);
|
||||
if (state == GLFW_PRESS)
|
||||
{
|
||||
currentHue += 0.001f;
|
||||
}
|
||||
if (currentHue > 1.0) currentHue = 0.0f;
|
||||
|
||||
// clear colour and depth buffer
|
||||
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
|
||||
|
||||
// select program
|
||||
glUseProgram(program);
|
||||
|
||||
// build view matrix
|
||||
mat4 viewMatrix;
|
||||
|
||||
// mat4Identity(viewMatrix);
|
||||
vec3 cameraPos = {0.0f, 1.0f, 1.3f};
|
||||
vec3 cameraLookAt = {0.0f, 0.2f, 0.0f};
|
||||
vec3 cameraPos = {cos(currentHue * 6 * M_PI) * 3.0f, 3.0f + sin(currentHue * 12 * M_PI) * 0.5, sin(currentHue * 6 * M_PI) * 3.0f};
|
||||
vec3 cameraLookAt = {0.0f, 0.0f, 0.0f};
|
||||
vec3 cameraUp = {0.0f, 1.0f, 0.0f};
|
||||
mat4BuildLookAt(viewMatrix, cameraPos, cameraLookAt, cameraUp);
|
||||
|
||||
|
||||
vec3 virtualCameraPosition = {1.5f, 1.0f, 1.0f};
|
||||
vec3 virtualCameraLookAt = {0.0f, 0.0f, -1.0f};
|
||||
|
||||
// calculate virtual lookAt and projection
|
||||
mat4 virtualCameraMatrix;
|
||||
mat4 virtualProjectionMatrix;
|
||||
mat4BuildLookAt(virtualCameraMatrix, virtualCameraPosition, virtualCameraLookAt, cameraUp);
|
||||
mat4BuildPerspective(virtualProjectionMatrix, 60 * M_PI / 180, aspect, 1, 4);
|
||||
|
||||
mat4 viewFrustumModelView;
|
||||
mat4Inverse(viewFrustumModelView, virtualProjectionMatrix);
|
||||
|
||||
mat3 mat3CameraRotationMatrix;
|
||||
mat3From4(mat3CameraRotationMatrix, virtualCameraMatrix);
|
||||
mat3Inverse(mat3CameraRotationMatrix, mat3CameraRotationMatrix);
|
||||
mat4 cameraRotationMatrix;
|
||||
mat4From3(cameraRotationMatrix, mat3CameraRotationMatrix);
|
||||
|
||||
mat4Interpolate(projectionMatrix, virtualProjectionMatrix, realProjectionMatrix, mapTo01(currentHue, 0.1f, 0.15f));
|
||||
mat4Interpolate(viewMatrix, virtualCameraMatrix, viewMatrix, mapTo01(currentHue, 0.1f, 0.15f));
|
||||
|
||||
mat4Interpolate(projectionMatrix, projectionMatrix, virtualProjectionMatrix, mapTo01(currentHue, 0.7f, 0.75f));
|
||||
mat4Interpolate(viewMatrix, viewMatrix, virtualCameraMatrix, mapTo01(currentHue, 0.7f, 0.75f));
|
||||
|
||||
mat4Interpolate(virtualCameraMatrix, identity, virtualCameraMatrix, mapTo01(currentHue, 0.3f, 0.35f));
|
||||
mat4Interpolate(virtualProjectionMatrix, identity, virtualProjectionMatrix, mapTo01(currentHue, 0.4f, 0.45f) * mapTo01(currentHue, 0.4f, 0.45f));
|
||||
|
||||
mat4Interpolate(virtualCameraMatrix, virtualCameraMatrix, identity, mapTo01(currentHue, 0.7f, 0.75f));
|
||||
mat4Interpolate(virtualProjectionMatrix, virtualProjectionMatrix, identity, mapTo01(currentHue, 0.7f, 0.75f));
|
||||
|
||||
|
||||
|
||||
glUseProgram(program);
|
||||
|
||||
GLuint brightnessLocation = glGetUniformLocation(program, "uBrightness");
|
||||
|
||||
GLuint projectionLocation = glGetUniformLocation(program, "uProjection");
|
||||
glUniformMatrix4fv(projectionLocation, 1, GL_FALSE, projectionMatrix);
|
||||
|
||||
|
||||
// build model Matrix
|
||||
// cubes.
|
||||
mat4 modelMatrix;
|
||||
vec3 scale;
|
||||
vec3 position;
|
||||
|
||||
float scales[] = {0.5f, 0.4f, 0.3f, 0.2f, 0.1f, 0.09f, 0.08f, 0.07f, 0.06f, 0.05f};
|
||||
for (int i = 0; i < 10; i++) {
|
||||
mat4Identity(modelMatrix);
|
||||
// cube 1
|
||||
mat4Identity(modelMatrix);
|
||||
|
||||
vec3Set(scale, scales[i], 0.05f, scales[i]);
|
||||
mat4Scale(modelMatrix, modelMatrix, scale);
|
||||
vec3Set(scale, 0.5f, 0.5f, 0.5f);
|
||||
mat4Scale(modelMatrix, modelMatrix, scale);
|
||||
|
||||
mat4RotateY(modelMatrix, modelMatrix, currentHue * 2 * M_PI + (i / 5.0f * M_PI));
|
||||
mat4RotateY(modelMatrix, modelMatrix, 0.5f);
|
||||
|
||||
vec3Set(position, 0.0f, i * 0.05f, 0.0f);
|
||||
mat4Translate(modelMatrix, modelMatrix, position);
|
||||
vec3Set(position, -0.3f, 0.5f, -0.4f);
|
||||
mat4Translate(modelMatrix, modelMatrix, position);
|
||||
|
||||
drawCube(position, modelMatrix, viewMatrix);
|
||||
mat4Multiply(modelMatrix, virtualCameraMatrix, modelMatrix);
|
||||
mat4Multiply(modelMatrix, virtualProjectionMatrix, modelMatrix);
|
||||
|
||||
glUniform1f(brightnessLocation, 1.0f);
|
||||
drawCube(modelMatrix, viewMatrix);
|
||||
|
||||
// cube 2
|
||||
mat4Identity(modelMatrix);
|
||||
|
||||
vec3Set(scale, 0.3f, 0.3f, 0.3f);
|
||||
mat4Scale(modelMatrix, modelMatrix, scale);
|
||||
|
||||
mat4RotateY(modelMatrix, modelMatrix, 0.5f);
|
||||
|
||||
vec3Set(position, -0.9f, 0.3f, -3.8f);
|
||||
mat4Translate(modelMatrix, modelMatrix, position);
|
||||
|
||||
mat4Multiply(modelMatrix, virtualCameraMatrix, modelMatrix);
|
||||
mat4Multiply(modelMatrix, virtualProjectionMatrix, modelMatrix);
|
||||
|
||||
glUniform1f(brightnessLocation, 1.0f);
|
||||
drawCube(modelMatrix, viewMatrix);
|
||||
|
||||
|
||||
// draw virtual camera
|
||||
mat4Identity(modelMatrix);
|
||||
|
||||
vec3Set(scale, 0.2f, 0.15f, 0.05f);
|
||||
mat4Scale(modelMatrix, modelMatrix, scale);
|
||||
|
||||
// apply rotations to camera
|
||||
|
||||
mat4Multiply(modelMatrix, cameraRotationMatrix, modelMatrix);
|
||||
|
||||
mat4Translate(modelMatrix, modelMatrix, virtualCameraPosition);
|
||||
mat4Multiply(modelMatrix, virtualCameraMatrix, modelMatrix);
|
||||
|
||||
glUniform1f(brightnessLocation, 0.0f);
|
||||
|
||||
if (currentHue < 0.37f) {
|
||||
drawCube(modelMatrix, viewMatrix);
|
||||
}
|
||||
|
||||
|
||||
|
||||
glUseProgram(originProgram);
|
||||
|
||||
projectionLocation = glGetUniformLocation(originProgram, "uProjection");
|
||||
glUniformMatrix4fv(projectionLocation, 1, GL_FALSE, projectionMatrix);
|
||||
|
||||
GLuint modelViewLocation = glGetUniformLocation(originProgram, "uModelView");
|
||||
glUniformMatrix4fv(modelViewLocation, 1, GL_FALSE, viewMatrix);
|
||||
|
||||
glBindVertexArray(originVAO);
|
||||
glLineWidth(5.0f);
|
||||
glDrawArrays(GL_LINES, 0, 6);
|
||||
|
||||
if (currentHue > 0.35f && currentHue < 0.65) {
|
||||
mat4Multiply(viewFrustumModelView, virtualProjectionMatrix, viewFrustumModelView);
|
||||
mat4Multiply(viewFrustumModelView, viewMatrix, viewFrustumModelView);
|
||||
|
||||
glUniformMatrix4fv(modelViewLocation, 1, GL_FALSE, viewFrustumModelView);
|
||||
|
||||
glBindVertexArray(vertexArrayObject);
|
||||
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, lineIndexBuffer);
|
||||
glDrawElements(GL_LINES, 24, GL_UNSIGNED_INT, 0);
|
||||
}
|
||||
|
||||
// draw floor
|
||||
glUseProgram(floorProgram);
|
||||
glBindVertexArray(vertexArrayObject);
|
||||
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, floorIndexBuffer);
|
||||
|
||||
glUniformMatrix4fv(glGetUniformLocation(floorProgram, "uView"), 1, GL_FALSE, viewMatrix);
|
||||
glUniformMatrix4fv(glGetUniformLocation(floorProgram, "uProjection"), 1, GL_FALSE, projectionMatrix);
|
||||
|
||||
mat4 floorModelMatrix;
|
||||
vec3 floorScale;
|
||||
mat4Identity(floorModelMatrix);
|
||||
vec3Set(floorScale, 10.0f, 0.01f, 10.0f);
|
||||
mat4Scale(floorModelMatrix, floorModelMatrix, floorScale);
|
||||
|
||||
glUniformMatrix4fv(glGetUniformLocation(floorProgram, "uModel"), 1, GL_FALSE, floorModelMatrix);
|
||||
|
||||
glDepthMask(GL_FALSE);
|
||||
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
|
||||
glDepthMask(GL_TRUE);
|
||||
|
||||
|
||||
}
|
||||
|
||||
void framebuffer_size_callback(GLFWwindow* window, int width, int height) {
|
||||
|
|
@ -303,9 +550,7 @@ int main(int argc, char const *argv[])
|
|||
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
|
||||
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
|
||||
|
||||
glfwWindowHint(GLFW_TRANSPARENT_FRAMEBUFFER , GLFW_TRUE);
|
||||
|
||||
GLFWwindow* window = glfwCreateWindow(initialWindowWidth, initialWindowHeight, "CG1", NULL, NULL);
|
||||
window = glfwCreateWindow(initialWindowWidth, initialWindowHeight, "CG1", NULL, NULL);
|
||||
|
||||
aspect = (float)initialWindowWidth / initialWindowHeight;
|
||||
if (!window) {
|
||||
|
|
|
|||
|
|
@ -0,0 +1,8 @@
|
|||
#version 330 core
|
||||
|
||||
in vec4 vPosition;
|
||||
|
||||
void main() {
|
||||
gl_FragColor = mix(vec4(1,1,1,0.5), vec4(0.8,0.8,0.8,0.5), step(0, sin(vPosition.x * 3.14159) * sin(vPosition.z * 3.14159)));
|
||||
// gl_FragColor = vec4(1,0,0,1);
|
||||
}
|
||||
|
|
@ -0,0 +1,14 @@
|
|||
#version 330 core
|
||||
|
||||
layout (location = 0) in vec3 aPosition;
|
||||
|
||||
uniform mat4 uModel;
|
||||
uniform mat4 uView;
|
||||
uniform mat4 uProjection;
|
||||
|
||||
out vec4 vPosition;
|
||||
|
||||
void main() {
|
||||
vPosition = uModel * vec4(aPosition, 1);
|
||||
gl_Position = uProjection * uView * vPosition;
|
||||
}
|
||||
|
|
@ -8,8 +8,10 @@ vec3 colors[6] = vec3[6](
|
|||
vec3(0.5, 1.0, 1.0)
|
||||
);
|
||||
|
||||
uniform float uBrightness;
|
||||
|
||||
void main() {
|
||||
// hacky solution to give each side a different colour
|
||||
int side = gl_PrimitiveID / 2;
|
||||
gl_FragColor = vec4(colors[side], 1.0);
|
||||
gl_FragColor = vec4(colors[side] * uBrightness, 1.0);
|
||||
}
|
||||
|
|
@ -0,0 +1,7 @@
|
|||
#version 330 core
|
||||
|
||||
in vec3 vertexColor;
|
||||
|
||||
void main() {
|
||||
gl_FragColor = vec4(vertexColor, 1.0);
|
||||
}
|
||||
|
|
@ -0,0 +1,13 @@
|
|||
#version 330 core
|
||||
layout (location = 0) in vec3 aPosition;
|
||||
layout (location = 1) in vec3 aColor;
|
||||
|
||||
uniform mat4 uModelView;
|
||||
uniform mat4 uProjection;
|
||||
|
||||
out vec3 vertexColor;
|
||||
|
||||
void main() {
|
||||
vertexColor = aColor;
|
||||
gl_Position = uProjection * uModelView * vec4(aPosition, 1.0);
|
||||
}
|
||||
Loading…
Reference in New Issue